Multiple PDF files often become too large due to high-resolution images, scanned pages, or large screenshots, making them inconvenient to upload, send, and archive. This article takes HeSoft Doc Batch Tool as an example to introduce how to use the "PDF Optimization and Compression" function to batch reduce image quality and resolution in PDFs, thereby reducing the file size of multiple PDF files, and to help users understand the compression effect through a comparison of file sizes before and after processing.
In daily office work, PDF files are often used to store contracts, reports, bids, scanned documents, product materials, and illustrated instructions. The problem is that whenever a PDF contains numerous high-definition images, scanned pictures, or screenshots, the file size tends to grow easily. A file size of a few MB is acceptable, but if you need to organize dozens or even hundreds of PDFs at once, opening each one individually to compress images is not only time-consuming but also prone to omissions.
The problem this article aims to solve is clear: how to batch-optimize and compress images within many PDF files to reduce file size. The office software used here is HeSoft Doc Batch Tool . As can be seen from its interface, it is positioned as batch processing software for files such as documents, PDFs, images, and text. Its core value is centralizing repetitive file operations into one workflow to reduce manual operation time.
Below, we will use screenshots to explain the complete process, from selecting the function, importing PDFs, and setting image quality and maximum resolution, to viewing the processing results. This article will not introduce extra features not shown in the screenshots, focusing solely on the "PDF Optimization & Compression" function.
Applicable Scenarios: Which PDFs Are Suitable for Batch Optimization and Compression
Batch compression of PDF images is suitable for many office scenarios, especially the following types:
1. Scanned PDF files with excessively large file sizes. For example, scanned contracts, invoices, archives, and certificate materials usually consist of images on every page. If the scanning resolution is high, the PDF volume will increase significantly. By reducing image quality or limiting the maximum image resolution, you can reduce file size while ensuring readability.
2. Illustrated reports, proposals, and bids that need to be sent. Many Word, docx, PPT, and image files are ultimately exported as PDFs. If they contain many high-definition product images, screenshots, or promotional pictures, the PDF might exceed the size limits for email attachments, system uploads, or online submission.
3. Saving space for file archiving. Enterprise archiving often involves handling not just one PDF, but a batch of project files, contracts, or a set of documents. Through batch optimization and compression, you can reduce overall storage usage, facilitating backup and transmission.
4. Multiple PDFs requiring a unified processing standard. When compressing manually one by one, the settings for each file might be inconsistent; using a batch processing workflow allows a group of PDFs to use the same set of image quality and resolution parameters, resulting in more uniform output.
Note that the compression effect on a PDF is related to its content. If a PDF mainly consists of images, the potential for compression is usually larger; if the PDF is already compressed or mainly contains text and vector content, the reduction in size might not be significant.
Effect Preview: Large PDF File Sizes Before Processing
First, look at the file list before processing. The screenshot shows 5 PDF files, named 1.pdf, 2.pdf, 3.pdf, 4.pdf, and 5.pdf. The file sizes are marked 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.
From this pre-processing state, you can see significant differences in file sizes among the PDFs. Some files are already small, like 4.pdf at just 49 KB; others are noticeably large, like 1.pdf and 5.pdf. In actual office work, if these PDFs need to be uploaded to a system, sent to clients, or organized for archiving, larger files mean longer waiting times and a higher chance of encountering attachment size limits.
Therefore, the significance of batch compression is not just to compress one file, but to allow a group of PDFs to be optimized simultaneously, avoiding the need to repeatedly open, save as, export, or regenerate PDFs.
Operation Step 1: Enter PDF Tools and Select "PDF Optimization & Compression"
After opening HeSoft Doc Batch Tool , you can see various tool categories on the left side, including Word Tools, Excel Tools, PowerPoint Tools, PDF Tools, Text Tools, Image Tools, etc. Since we need to process PDF files this time, first enter the PDF Tools category on the left.
In the PDF Tools list, find and click "25, PDF Optimization & Compression". In the screenshot, this function card is selected, indicating it is used to "batch optimize and compress PDF files, reducing file size."
The purpose of this step is to select the correct batch processing function. HeSoft Doc Batch Tool also includes functions like converting PDF pages to image format, deleting blank PDF pages, converting PDF to Word, and converting PDF to JPG images. But this time, our goal is not format conversion, but rather compressing the images within the PDF files to make the PDF files smaller in size, so we should select "PDF Optimization & Compression."
The expected result is: after entering this function, the software will open a wizard-style processing page, where you can follow the subsequent steps to import files, set processing options, set the save location, and start processing.
Operation Step 2: Add PDF Files to be Batch Compressed
After entering "PDF Optimization & Compression," the current function name is displayed at the top of the page, and the process is divided into several steps: select records to process, set processing options, set save location, and start processing. The screenshot currently shows step 1, "Select records to process."
In the upper right area of the page, you can see buttons like Add File(s), Import Files from Folder, Clear, and More. For a small number of PDFs, you can use "Add File(s)"; if PDF files are concentrated in one folder, using "Import Files from Folder" is more suitable for batch office scenarios.
In the screenshot, 5 PDF files have already been imported. The table lists information such as serial number, name, path, extension, creation time, and modification time. You can see the file path is located in D:\test\ and the extensions are all pdf, indicating these files have been added to the current batch processing queue.
The operational purpose of this step is to confirm which PDFs will be processed. Before proceeding, it is recommended to check the file names and paths in the table to avoid adding PDFs that shouldn't be compressed to the queue. If an import error occurs, you can remove individual records using the delete icon in the operation column; if you need to reselect, you can also use "Clear" and then import again.
After confirming the file list is correct, click the Next button at the bottom to enter the processing parameter settings.
Operation Step 3: Setting Image Quality and Maximum Image Resolution
After entering step 2, "Set processing options," you can see parameters related to PDF image compression. The screenshot mainly includes three options: Image Quality (1~100), Maximum Image Resolution (PPI), and Font Embedding Method.
Among them, image quality is a crucial parameter affecting PDF file size. In the screenshot, the image quality is set to 60%, indicating that the software will optimize the images within the PDF according to this quality parameter. Generally speaking, lower values lead to greater compression and potentially smaller file sizes, but image clarity might also decrease; higher values preserve better image quality, but the compressed file size might be larger.
The Maximum Image Resolution (PPI) is used to limit the highest resolution of the images. In the screenshot, it is set to 72. For many PDFs intended only for screen viewing, email transmission, or general office reading, an excessively high image resolution is often unnecessary. Limiting the PPI can reduce the space occupied by images in the PDF.
The font embedding method also appears in the screenshot, but our current focus is on optimizing images within the PDF. Unless you clearly understand the impact of font embedding on file compatibility and display effects, it is advisable to cautiously adjust settings unrelated to image compression.
The expected result of this step is to uniformly apply the image compression parameters to all imported PDF files. This way, you don't need to open each PDF individually to set the compression ratio, significantly reducing repetitive labor.
Operation Step 4: Set the Save Location and Start Processing
After setting the image quality and maximum image resolution, click the Next button at the bottom. Following the page flow, you will subsequently enter "Set save location" and "Start processing." The roles of these two steps are to specify the output location for the compressed PDF files and to execute the batch processing task, respectively.
In an office scenario, it is recommended to save the compressed files into a new folder, such as creating a separate "Compressed PDFs" directory. This prevents the files before and after processing from being mixed up, making it easier to compare file sizes. If the software offers a choice between overwriting original files or saving as a copy, you should choose carefully according to your backup habits; before confirming the results, keeping the original files is more recommended.
Once "Start processing" is entered, the batch optimization and compression is executed. During processing, the software will handle the PDFs one by one according to the previously imported file list. Since this is a batch processing workflow, users do not need to repeatedly click compress, save, close, etc., for each file, making it suitable for handling multiple files at once.
Effect Preview: Significantly Reduced PDF File Size After Processing
After the processing is complete, check the output files. The screenshot again shows 1.pdf through 5.pdf, with the processed file sizes marked in a red box on the right: 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.
Compared to before processing, the file sizes of several files have decreased to varying degrees. For example, 1.pdf decreased from 6,538 KB to 2,733 KB; 5.pdf decreased from 3,830 KB to 1,279 KB; 3.pdf decreased from 614 KB to 134 KB. 4.pdf was originally relatively small, so its decrease was relatively limited, but it still went from 49 KB down to 35 KB.
This illustrates that batch optimizing images in PDFs can effectively reduce file sizes. However, the compression ratio is not completely consistent across different files because the number of images, image resolution, original compression state, and page content vary for each PDF.
Frequently Asked Questions and Notes
1. What is an appropriate setting for image quality? If the PDF is mainly used for screen viewing, email sending, or internal circulation, you can start testing with medium parameters like the 60% used in the screenshot example. If higher requirements for image clarity exist, you can increase the value appropriately; if you only need the content to be legible and have strict volume limits, you can try lower values after backing up the original files.
2. Is a lower PPI setting always better? Not necessarily. Lower PPI might result in smaller images, but details could also be reduced. For general reading PDFs, 72 PPI is usually more suitable for screen viewing scenarios; if the file needs to be printed or retain more image details, you should set it cautiously based on actual requirements.
3. Why doesn't the size of some PDFs change much after compression? If the PDF itself is already compressed, or if the main content is text, vector graphics, or tables rather than large images, the reduction in volume might not be obvious. Batch compressing PDF images is most suitable for files with a high proportion of images.
4. Is a backup needed before processing? A backup is recommended. Although batch processing can greatly improve efficiency, it's best to keep the original PDFs in a separate folder and output the compression results to a new location to avoid operational errors.
5. How can I avoid selecting the wrong files during batch processing? Check the names, paths, and extensions in the file list at step 1. If you find files that do not need processing, remove them first before continuing. Confirming the file scope is especially important when handling project materials or contract documents.
Summary: Reduce Repetitive Work in PDF Compression with Batch Processing
When many PDF files become large due to containing too many images, compressing them one by one is not only inefficient but also detrimental to maintaining a unified processing standard. By using the "PDF Optimization & Compression" function of HeSoft Doc Batch Tool , you can import multiple PDFs at once, uniformly set image quality and maximum resolution, and then batch output the compressed files.
Judging from the example results, the file sizes of multiple PDFs decreased significantly after processing, making them more suitable for email sending, system uploading, data archiving, and shared transmission. If you also have a batch of scanned PDFs, graphic-rich PDFs, or large-size PDFs that need slimming down, it is suggested to first copy the original files as a backup, then follow the steps in this article for batch processing, quickly completing PDF image optimization and file size compression.