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Why Some PDF Files Cannot Be Reduced in Size and How to Fix It

Amos Gikunda Oct 22, 2026 868 views

Question details

The user wants to understand why some large PDF files generated from design software can be significantly reduced in size, while others cannot be compressed further.

Why Some PDF Files Cannot Be Reduced in Size and How to Fix It

Product: PDF
Device & OS: not provided
Scenario: Attempting to compress and reduce the file size of exported PDF documents for sharing or storage.
Observed behavior: Some PDF files successfully shrink in size upon compression, while other PDFs maintain a bloated file size regardless of the reduction attempts.

Before you start

Before applying compression techniques, review the PDF to ensure it contains high-resolution assets that can actually be compressed, and verify you are not overwriting your original high-quality design file.

Solution 1Recommended

Use the 'Save As' Function to Reclaim Unused Space

Using the 'Save As' command rewrites the entire document, removing deleted objects and reclaiming space that standard saving leaves behind.

When working with PDFs, simply clicking 'Save' appends new changes to the file, which preserves editing history and deleted data, often increasing the overall file size. The 'Save As' command forces the software to rewrite the document from scratch, effectively discarding any unused or cached data.

Open the Document

Launch your PDF editor and open the large PDF file you wish to reduce in size.

Access the File Menu

Click on the 'File' menu located in the top-left corner of the application window.

Select Save As

Choose 'Save As' from the dropdown menu instead of the standard 'Save' option.

Save a New Copy

Select a destination folder, optionally rename your file to avoid overwriting the original, and click 'Save' to generate the optimized document.

Use the 'Save As' Function to Reclaim Unused Space

Pro Tip: Using 'Save As' is most effective after you have made major edits, deletions, or asset replacements within your PDF.

Solution 2

Optimize Assets Before Exporting Source Files

If your PDF originates from design software like InDesign, the best way to ensure a manageable file size is to optimize images, vector graphics, and fonts before exporting.

PDF Optimization Tool

Easily Compress Large PDFs with WPS Office

If you are struggling with oversized PDFs, WPS Office features a dedicated PDF compression tool that intelligently reduces file size while preserving document quality, making it much easier to email and upload files.

1. Open PDF in WPS Office: Launch WPS Office and open the oversized PDF document you want to compress.
2. Navigate to the Tools Tab: Click on the 'Tools' tab located in the top navigation ribbon.
3. Select PDF Compressor: Click on the 'Compress' or 'PDF Compressor' button to open the compression settings dialog.
4. Choose Compression Level: Select your desired compression level based on your quality needs, then click 'Compress' to instantly shrink the file.

Dedicated PDF compression tool with customizable quality settings (HD, Normal, Common).Preserves the visual integrity of images, fonts, and graphics during size reduction.Ensures full format compatibility with standard Adobe PDF files.Lightweight, free-to-use software suite tailored for seamless document management.

microsoft office alternative - wps office

Frequently Asked Questions

Why do some PDFs not shrink even when using a compression tool?

If a PDF is already highly optimized or consists almost entirely of plain text and basic vector shapes, compression tools will not be able to reduce the size much further. Compression primarily targets high-resolution images and embedded fonts.

Does hitting 'Save' repeatedly increase my PDF file size?

Yes. When you use the standard 'Save' function, many PDF editors append the new changes to the end of the file rather than rewriting it. This preserves editing history and deleted elements, which can bloat the file size over time.

How can I reduce a PDF's size without sacrificing image quality?

You can use advanced PDF tools like WPS Office that offer variable compression levels. By choosing an 'HD' compression setting, the software optimizes background data and metadata while keeping images visually crisp and clear.

PDF Troubleshooting