Scanned PDFs are usually composed of full-page images, making their file sizes more prone to increase compared to regular text-based PDFs. This article explains how to use the "PDF Optimization and Compression" feature in HeSoft Doc Batch Tool to batch reduce PDF image quality and limit the maximum image resolution, import multiple PDF files at once and process them uniformly, helping users quickly reduce PDF size and improve efficiency for sending, uploading, and archiving.
Many people encounter the same issue when organizing scanned PDFs: the file appears to be just a few pages of contracts, manuals, or documents, but the file size is very large. The reason usually lies not in the text, but in the images. Scanned PDFs often save each page as an image; the higher the resolution and the richer the colors, the larger the PDF file. If a batch of files needs to be sent or uploaded, compressing them one by one wastes a lot of time.
This article introduces a method more suitable for office scenarios: using HeSoft Doc Batch Tool to batch optimize and compress images in PDFs. This software is a batch processing tool for office documents, suitable for handling common file types such as PDF, Word, Excel, PowerPoint, images, and text. Its value lies not in processing a single file, but in turning many repetitive operations into a single batch task.
The following sections will explain how to batch reduce PDF image quality, set maximum image resolution, and ultimately decrease the file size of multiple PDFs, through a comparison of file sizes before and after processing, as well as screenshots of the software operation.
Applicable Scenarios: Scanned Documents, Graphic Materials, and Archived PDFs Can All Be Handled This Way
Batch compressing PDF images is not only applicable to one type of file. As long as the PDF volume is mainly caused by images, you can consider using "PDF Optimization and Compression". Common scenarios include:
Scanned Contracts and Archives. Scanned contracts, stamped documents, certificate materials, and paper archives are often saved as PDFs. If the scanner uses a high resolution by default, the file size will increase rapidly. Batch compression can make these PDFs easier to archive and transfer.
Project Materials and Reports. Many proposals, product manuals, and design documents contain a large number of images. Even if the original content comes from Word, doc, docx, PPT, or images, it may still be inconvenient to send after exporting to PDF due to large image sizes.
System Upload Limits. Many business systems, bidding platforms, expense systems, and OA processes have size limits for attachments. For example, a single PDF might not exceed a certain MB size. Manually compressing multiple files in this situation is very inefficient; batch processing is more suitable.
Long-term Storage and Backup. As corporate files increase, the storage space for PDF archives continues to grow. Reasonable compression of image-based PDFs can reduce disk usage and facilitate cloud sync and backup.
It should be emphasized that compressing PDF images is a "balance between file size and clarity". If the file is for formal printing or requires retained image details, parameters should be chosen more cautiously; if it's only for reading, circulation, and uploading, appropriately reducing image quality usually results in significant size reduction.
Effect Preview: Multiple PDFs of Different Sizes but Overall Large Before Processing
Below is the file list before processing. You can see the sizes of the 5 PDF files are 6,538 KB, 3,094 KB, 614 KB, 49 KB, and 3,830 KB respectively. The file volumes are marked by red boxes on the right, indicating that some PDFs have reached several MBs.
From an office perspective, sending a single PDF around 6 MB might not be a big problem, but if a project has dozens of similar files, the accumulated size becomes very large. More troublesome is that many platforms limit the size of individual attachments, not the total size; when a PDF file exceeds the limit, it must be compressed before uploading.
The variation in file sizes also suggests that not all files will have the same effect during batch compression. PDFs with many high-resolution, insufficiently compressed images usually show a more significant reduction; already small PDFs have a relatively limited reduction.
Step One: Find "PDF Optimization and Compression" in PDF Tools
After opening HeSoft Doc Batch Tool , first select PDF Tools in the left function category. The screenshot shows various tool categories listed in the left menu, with PDF Tools being selected. The right side displays a set of PDF-related function cards, including page processing, format conversion, deleting blank pages, etc.
The function needed this time is "25. PDF Optimization and Compression". The card description says it's for batch optimizing and compressing PDF files, reducing file size. Click this card to enter the corresponding function.
Be careful not to select the wrong function in this step. For example, "PDF to Word" is suitable for converting PDF to Word format, and "PDF to JPG Images" is for exporting images, not compressing the PDF itself. If the goal is to reduce the PDF file size, you should enter "PDF Optimization and Compression".
Once done, the software will enter a step-by-step processing interface where you will proceed to import files, configure processing options, set the save location, and start processing.
Step Two: Import the List of PDF Files to Be Compressed
After entering "PDF Optimization and Compression", the first step is: Select records to process. You can see the function name at the top of the screenshot, with buttons provided on the right like Add File and Import Files from Folder.
If you only need to process a few PDFs, you can click "Add Files" to select them one by one; if the PDFs are already placed in a single directory, it is recommended to use "Import Files from Folder", which better suits the habit of batch processing. In the screenshot, 5 PDFs have been imported, with names, paths, extensions, creation times, modification times, and other information listed in the table.
The purpose of this step is not to compress immediately, but to create a processing queue. Users should check if the files in the table are correct, e.g., confirming the extension is pdf, the path is the expected folder, and there are no files that shouldn't be processed. If there are errors, the delete icon in the action column can be used to remove corresponding records; if the imported range is entirely wrong, "Clear" can be used before re-adding files.
After confirming accuracy, click "Next" at the bottom of the page to proceed to the parameter settings page.
Step Three: Control Compression Strength via Image Quality
The second step is "Set Processing Options". As seen in the screenshot, the image quality option is enabled, with the parameter range shown as 1~100, the current input value is 60, accompanied by a percent sign. This indicates that this batch processing will optimize images in the PDF at 60% image quality.
Image quality is key to the compression effect. For PDFs containing photos, scans, or screenshots, reducing image quality can often significantly decrease file size. Usually, the lower the value, the stronger the compression; the higher the value, the more clarity is preserved. The value of 60% in the screenshot can be considered a relatively general setting, suitable for an initial test.
If the text in the PDF is part of the scanned image, a quality setting that is too low might affect the clarity of text edges. Therefore, it is recommended to select one or two representative PDFs for testing before formally processing a large number of files, to ensure the compressed result is acceptable for reading, before batch processing all files.
For materials submitted for review, internal circulation, or e-mailing, it's usually sufficient as long as the text is clear and images are recognizable; for design drafts, detailed product images, or materials needing printing, quality parameters should be appropriately increased.
Step Four: Limit Maximum Image Resolution to Reduce Inefficient Volume
Besides image quality, the screenshot also shows the Max Image Resolution (PPI) option, currently set to 72. PPI can be understood as the resolution cap retained for images in the PDF. Many scans or graphic PDFs have image resolutions much higher than needed for screen viewing; retaining them directly leads to unnecessarily large files.
The purpose of setting the maximum image resolution is to compress images exceeding the limit into a range more suitable for the usage scenario. For PDFs intended only for viewing on computers, phones, or tablets, a lower PPI is often sufficient for reading; for PDFs requiring high-definition printing, it should not be blindly reduced.
The screenshot also shows a "Font Embedding Method" option, but this is not central to image compression this time. If you are unfamiliar with the relationship between font embedding and PDF display compatibility, it's advisable not to arbitrarily adjust parameters unrelated to image compression, to avoid affecting the file's appearance.
Continue by clicking "Next" after configuring settings. Following the interface flow, the next pages will be "Set Save Location" and "Start Processing". It is recommended to select a new output location to save the compressed PDFs; this facilitates comparison with the original files and keeps the originals as a backup.
Post-Processing Effect: Reduced File Sizes More Suitable for Transfer and Archiving
After the batch process is complete, review the list of processed PDF files. The screenshot shows the 5 files have changed to sizes of 2,733 KB, 2,722 KB, 134 KB, 35 KB, and 1,279 KB respectively.
Comparing with before processing, we can see that 1.pdf dropped from 6,538 KB to 2,733 KB, 5.pdf from 3,830 KB to 1,279 KB, and 3.pdf from 614 KB to 134 KB. This kind of size reduction is very practical for files needing batch uploading or sending. Even if each file only decreases by a few hundred KB, when the number of files reaches dozens or hundreds, the overall space and time saved are considerable.
After processing, it is recommended to open several compressed PDFs for a spot-check of the display effect, focusing on whether scanned text is clear and image details meet usage requirements. If insufficient clarity is found, you can return to the processing options, appropriately increase the image quality or PPI, and reprocess.
Common Questions and Considerations
1. Will batch compression change the PDF content? The goal of this process is to optimize and compress PDFs, focusing on reducing file size. Compressing images may affect image clarity, but generally does not change the file's page count or basic content. Spot-checking after completion is still recommended.
2. Why do compression ratios vary greatly for PDFs in the same batch? Because the content of each PDF is different. Some files are composed of high-definition images, offering large compression potential; others may already be very small, or consist mostly of text content, leaving limited room for compression.
3. Is backing up necessary before processing? Backing up is strongly recommended, especially for important documents like contracts, archives, and reimbursement vouchers. The safest method is to save the compressed results to a new folder, not directly overwriting the original PDFs.
4. What if the scanned text becomes blurry? You can increase the image quality value or increase the maximum image resolution. Don't solely pursue the smallest file size; choose parameters based on actual usage needs like reading, printing, or submission.
5. Can a large number of PDFs be processed at once? From the screenshot process, this function supports importing multiple PDF records for batch processing. The actual processing quantity can be arranged based on computer performance, file size, and task requirements. For a large number of files, it is advisable to process them in batches and check the results.
Summary: Batch Processing is More Suitable for Compressing Scanned PDFs
The large size of scanned PDFs is essentially often due to large images. Using the "PDF Optimization and Compression" feature of HeSoft Doc Batch Tool , you can import multiple PDFs at once and batch reduce file size by setting image quality and maximum image resolution. Compared to opening and compressing PDFs one by one, this method saves time and makes it easier to maintain a consistent standard.
If you are processing scanned contracts, project materials, graphic reports, or archived PDFs, it is recommended to select a few files first to test parameters. After confirming the clarity meets requirements, then batch process all files. This way, you can reduce PDF sizes while decreasing repetitive work, making file sending, uploading, and archiving more efficient.