When multiple PDF files are too large due to scanned images, high-definition screenshots, or product photos, compressing them one by one wastes a lot of time. This article explains how to use the "PDF Optimization and Compression" feature of HeSoft Doc Batch Tool to batch import PDF files, uniformly set image quality and maximum PPI, and then output the compressed PDFs. The article includes a before-and-after file size comparison, detailed steps, and parameter considerations, suitable for office upload, email sending, and data archiving scenarios.
In office document workflows, PDF offers great compatibility, but "file too large" is also one of the most common issues. Especially for scanned copies, illustrated reports, training materials, product manuals, and photos converted to PDF, a single file often reaches several MB. When sending or uploading multiple files together, it's easy to exceed platform limits. Many people open a PDF, compress it once, save it as a new file, and then move on to the next. This approach is acceptable when dealing with only a few files, but once faced with a whole batch of PDFs, it becomes typical repetitive labor.
This article introduces a processing method more suitable for office scenarios: using the PDF Optimization and Compression function in HeSoft Doc Batch Tool to batch optimize images in multiple PDF files. By uniformly lowering image quality and limiting the maximum image resolution (PPI), it achieves the goal of reducing PDF file size. It is an office software designed for batch file processing, whose core value lies in streamlining and batching repetitive steps, saving users from mechanical operations and freeing up time for more important work.
We will first look at the size change before and after processing, and then explain the operating steps according to software screenshots. Even if you have not used this type of batch PDF compression tool before, you can follow the process in this article to complete the task.
Applicable Scenarios: Why Batch Reduce Image Size in PDFs
The most common source of excessively large PDF files is images. For instance, a contract scanned by a scanner essentially has each page as an image; materials organized by taking photos with a mobile phone retain high pixels when generated as PDFs; PDFs exported from PPT, Word, or image assets may also contain a large number of high-quality images if not optimized. For these files, simple ZIP compression often yields limited results, while directly optimizing the internal image resources of the PDF is more targeted.
Batch reducing PDF image quality and resolution is suitable for the following office scenarios:
- Batch submission of materials: Registration materials, audit documents, project application files, supplier qualification documents, etc., often require uploading PDFs with restrictions on individual file size or total attachment size.
- Batch sending emails: Roles in sales, administration, human resources, and finance frequently need to send multiple PDF attachments. Overly large files can cause sending failures or slow downloads for the recipient.
- Batch archiving of scanned copies: When contracts, invoices, receipts, and certificates are stored long-term, storage space will continuously increase if not compressed.
- Unified processing of team files: PDFs submitted by multiple people often have inconsistent parameters—some files are large, some are small. Unifying compression makes organization and distribution easier.
- Reducing repetitive operations: Processing dozens of PDFs at once is more stable and makes it easier to ensure consistent parameters than opening and saving each one individually.
For PDFs mainly composed of text, the compression effect may be limited; for image-based PDFs, scanned PDFs, and PDFs containing many screenshots, optimizing using image quality and PPI parameters usually yields more noticeable changes.
Effect Preview: File Size Comparison Before Compression
The screenshot before processing below shows the sizes of 5 PDF files awaiting compression. They are 1.pdf, 2.pdf, 3.pdf, 4.pdf, and 5.pdf. As seen in the red box on the right, 1.pdf is 6,538 KB, 2.pdf is 3,094 KB, 3.pdf is 614 KB, 4.pdf is 49 KB, and 5.pdf is 3,830 KB.
This set of files is quite representative: some PDFs are large, while others are already small. During batch compression, the compression ratio will not be exactly the same for all files. Generally, the larger the original image, the higher the resolution, and the less prior compression, the more noticeable the size reduction after optimization; conversely, even with further compression, a PDF that is already small may not shrink significantly.
If these files were processed manually one by one, you would need to repeat the process of opening, setting, and saving at least 5 times. In actual office work with 50 or 500 files, the time cost would be much higher, and it's very easy to miss a file or apply different parameter settings inadvertently.
Effect Preview: PDF Size Change After Compression
After processing with "PDF Optimization and Compression," the size of the same batch of files decreased significantly. In the processed screenshot, 1.pdf is 2,733 KB, 2.pdf is 2,722 KB, 3.pdf is 134 KB, 4.pdf is 35 KB, and 5.pdf is 1,279 KB.
Looking at individual files, 1.pdf decreased by about 3,805 KB, 5.pdf decreased by about 2,551 KB, and 3.pdf also dropped from 614 KB to 134 KB. Overall, the 5 files decreased from about 14,125 KB to about 6,903 KB, making the size compression effect very intuitive. For users needing to upload document packages or send email attachments, this change can effectively reduce failure rates and waiting times.
Of course, compression is not just about pursuing the smallest number. The processed PDF still needs to meet readability requirements, especially for text, signatures, seals, QR codes, and chart details in scanned files. Parameter setting suggestions and precautions will be introduced later in this article.
Operating Steps: Batch Compressing Images in Multiple PDF Files
The explanation below follows the actual workflow of the software interface. The product name in the screenshot is HeSoft Doc Batch Tool , and the version interface shows it offers various batch document processing functions. The function used this time is "PDF Optimization and Compression" within the PDF tools.
Step 1: Find "PDF Optimization and Compression" in the PDF Tools
After opening the software, the left side features a tool category navigation, including Home, Task Flows, All Tools, File Name, Folder Name, File Organization, Word Tools, Excel Tools, PowerPoint Tools, PDF Tools, etc. Since the goal this time is to process PDF files, you need to first click PDF Tools on the left.
In the function card area on the right, you can see multiple PDF-related functions, such as Convert PDF Pages to Image Format, Convert Color PDF to Black and White, Delete PDF Blank Pages, PDF to Word, PDF to PowerPoint, etc. What you need to select here is "25. PDF Optimization and Compression", whose description text is Batch optimize and compress PDF files, reduce file size.
The purpose of this step is to enter the functional module designed specifically for reducing PDF file size. Do not mistakenly select conversion functions like "PDF to Word" or "PDF to JPG Images," because what this article aims to do is preserve the PDF format while optimizing the image resources within it.
Step 2: Import the List of PDF Files to be Processed
After entering "PDF Optimization and Compression," the top of the page shows the process flow: Step 1 Select records to process, Step 2 Set processing options, Step 3 Set save location, Step 4 Start processing. The current interface is at Step 1.
In the upper right area, you can see buttons like Add Files, Import Files from Folder, Clear, and More. During actual use, if the PDFs are scattered in different locations, you can click "Add Files" to select them; if all PDFs to be processed are in the same folder, you can use "Import Files from Folder," which better aligns with the batch processing approach.
The screenshot already shows 5 imported PDF files, with the table listing information such as Name, Path, Extension, Creation Time, and Modification Time. The file paths are displayed as D:\test\1.pdf, D:\test\2.pdf, etc., all with the pdf extension. The record count shown at the bottom of the table is 5, indicating the current batch task contains 5 files.
After importing, it is recommended to do a quick check: confirm the file names are correct, confirm the extension is PDF, and confirm the paths come from the target folder. If you find an incorrect import, you can delete a record via the operation column; if the entire import is wrong, use "Clear" to reselect. After confirming everything is correct, click Next at the bottom.
Step 3: Enable Image Quality Setting to Control Compression Strength
After entering Step 2, "Set processing options," the first thing you see is Image Quality (1~100). In the screenshot, the switch on the left side of this item is enabled, and the input box is filled with 60, with the right unit shown as a percentage. This indicates that this batch process will optimize the images in the PDFs using the set image quality.
The image quality parameter can be understood as a balance between compression strength and clarity. Higher values typically preserve more image detail but may lead to larger file sizes; lower values make it easier to reduce file size, but the image might become blurry. The screenshot uses a value of 60%, suitable for many common reading, uploading, and archiving scenarios, representing a relatively balanced setting.
If your PDFs are standard scanned materials, supporting documents, or internal circulation files, you can start by trying around 60; for files containing high-definition product photos, design drafts, or those with high image detail requirements, you can increase it appropriately; if you only require legible text for system submission and the platform limits are very strict, you can test and then lower it further as needed.
Step 4: Set Maximum Image Resolution PPI to Further Reduce PDF Size
Below the image quality setting, you can see Maximum Image Resolution (PPI). In the screenshot, this item is also enabled, and the input box is set to 72. PPI is an important parameter affecting image display and print detail. For PDFs intended for screen viewing, 72 PPI can usually meet basic readability; for files destined for printing, magnified viewing, or detail preservation, a higher PPI may be necessary.
By limiting the maximum image resolution, excessively high-resolution images inside the PDF can be lowered to the specified range, thereby reducing the file's storage footprint. Many scanned originals have a high native resolution but are actually only used for online viewing or upload review, not requiring all pixels. In such cases, limiting PPI often leads to a significant size reduction.
The screenshot interface also shows Font Embedding Method, but this is not a core parameter for this session of "compressing PDF images." For most image-based PDFs, priority should be given to adjusting Image Quality and Maximum Image Resolution. Once set, click Next at the bottom to proceed to the save location setup.
Step 5: Select Output Location and Start Processing
The software flow shows Step 3 as "Set save location" and Step 4 as "Start processing." Although the provided screenshot doesn't show the save location page, judging from the process design, you need to specify the output location for the compressed files before batch processing. It's recommended to save the compressed PDFs into a new folder, such as "Compressed PDFs" or "Upload Version PDFs," and not mix them with the original files.
This has two benefits: first, it preserves the original PDFs, avoiding a situation where you find insufficient clarity after compression but cannot revert; second, it facilitates comparing file sizes before and after processing, quickly confirming the compression effect. After setting the save location, proceed to the start processing phase, where the software will batch compress all PDFs sequentially based on the previously imported file list and unified parameters.
Compared to manual processing, the biggest advantage of this workflow is "set once, execute for multiple files." Especially in batch file scenarios involving financial receipts, scanned contracts, project materials, training courseware, etc., it significantly reduces repetitive clicking and waiting time.
Parameter Selection Advice: How to Balance Size and Clarity
When batch compressing PDFs, many users are most concerned about two questions: how small the file can get, and whether it will become unreadable. In reality, there is no single answer for PDF compression parameters that fits all files; decisions should be based on the intended use.
- For email sending: A moderate compression setting is recommended first, such as image quality 60~70, PPI 72~120, trying to ensure a good reading experience while reducing size.
- For system uploads: If platform limits are strict, you can appropriately lower quality or PPI, but must check if critical content remains clear after compression.
- For long-term archiving: If future printing or review might be necessary, avoid excessive compression and preferably save the original files as well.
- For print output: Setting PPI too low is not recommended, to avoid unclear images, seals, or fine lines after printing.
- For pure reading materials: You can focus more on file size and appropriately lower image quality to improve transfer efficiency.
A better practice is to first select 2 to 3 representative PDFs for testing: include the largest file, the file with the most images, and the most important file. After processing, open them to check clarity, and then decide whether to apply the same parameters to all files. The benefit of a batch tool is that once parameters are determined, they can be quickly applied to the entire batch of PDFs without repeated manual configuration.
Common Questions and Precautions
1. Will the file names change after compression?
From the screenshots, the example files before and after processing are still displayed as 1.pdf, 2.pdf, 3.pdf, 4.pdf, 5.pdf. The actual saving method depends on your settings in the save location step. To avoid confusion, it's recommended to save the output files to a separate directory and verify them by file size and visual effect after processing.
2. Why didn't 2.pdf compress as much as 1.pdf and 5.pdf?
Different PDFs have different internal resources. 2.pdf decreased from 3,094 KB to 2,722 KB, suggesting it might already have had some compression or fewer optimizable image resources. Meanwhile, the more significant drop for 1.pdf and 5.pdf indicates they likely contained images with higher resolution or larger volume. Inconsistent results across a batch compression are normal.
3. Is an image quality setting of 60 always appropriate?
Not necessarily. 60 is the example value from the screenshot, suitable for many common office scenarios, but it does not mean all files should use the same value. Content like important documents, contract seals, QR codes, and drawing details needs checking after compression. If blurriness is found, you should increase the image quality or PPI and reprocess.
4. Can PPI be set very low?
PPI can be lowered to reduce size, but excessively low values can affect image details. Especially small-font text, table lines, and seal edges in scanned files might become unclear at a low PPI. It's recommended to choose based on the final use, rather than blindly aiming for the smallest file.
5. Is a backup necessary before batch processing?
A backup is recommended, especially for important files. The safest method is to keep the original folder unchanged and output the compression results to a new folder. Only use them for uploading, sending, or archiving after confirming all files open normally and the content is clear.
6. Is this method suitable for Word, docx, doc files?
This article introduces the optimization and compression of PDF files. If the original materials are Word documents, such as docx or doc, you usually need to first confirm if they should be exported as PDFs before performing PDF compression. The HeSoft Doc Batch Tool interface also has categories like Word Tools, but the steps in this article are only for the PDF Optimization and Compression function shown in the screenshots.
Summary: Batch Compress PDFs with Unified Parameters for Lighter File Transfer
When multiple PDF files are too large, opening and compressing them one by one is an inefficient approach. A method more suited to office scenarios is to use a batch processing tool to uniformly import files, uniformly set image quality and maximum resolution, and uniformly output the compressed PDFs. This not only reduces repetitive labor but also allows the entire batch of files to maintain a relatively consistent compression standard.
From the example results, the overall size of the 5 PDF files dropped from about 14,125 KB to about 6,903 KB, making the files much more suitable for email sending, system uploading, and document archiving. For users who frequently handle scans, contracts, reports, courseware, and image-based PDFs, the "PDF Optimization and Compression" function of HeSoft Doc Batch Tool can significantly improve processing efficiency.
If you have a batch of PDF files right now that are difficult to upload or send because their images are too large, it's recommended to first follow this article's workflow to import a small number of files for parameter testing. After confirming the clarity meets your requirements, proceed to batch process all files. Replacing multiple repetitive operations with a single setup is the true value of office software in boosting efficiency.