1. Step-by-step: get a PDF under 100KB
- Open the PDFNest Compress PDF tool.
- Drop in your PDF — it's compressed on your device, never uploaded.
- Choose a stronger compression level (more compression = smaller file, lower image quality).
- Download and check the size. If it's still over 100KB, compress again or reduce the source resolution (below).
Compress your PDF nowShrink it for forms and uploads — free, private, no watermark.
Compress PDF →2. Why your PDF is so large
A PDF that's only text is usually a few kilobytes. When a PDF balloons to megabytes, it's almost always images — especially scans, where every page is a full-resolution photo. So the size lever that matters most isn't "compression magic," it's image resolution: a page scanned at 600 DPI is roughly four times the data of the same page at 300 DPI, which is plenty for a form.
3. Hitting a strict target size
You can't dial in an exact byte count, but you can reliably get under a target:
- Start with the strongest compression level and check the result.
- If a form only needs to be readable (not printed), aggressive compression is fine — legibility, not crispness, is the goal.
- Remove pages you don't need with Remove Pages — fewer pages, smaller file.
- If it's a multi-page scan, even 150 DPI is usually readable on screen and dramatically smaller.
4. If it's a scanned document
Scans are the usual culprit behind "won't go under 100KB." Two things help most: lower the resolution, and convert colour scans to grayscale if colour isn't required (it roughly thirds the data). If you only need the text from the scan rather than the image, run it through OCR and save the text instead — a few kilobytes total. For the general approach, see compress a PDF without losing quality and reduce PDF size for email.
The bottom line
To get a PDF under 100KB: compress it, and if it's still too big, attack the real cause — image resolution. Use strong compression for screen-only forms, drop scans to 150–300 DPI, and trim unneeded pages. All free, all in your browser.
Frequently asked questions
How do I reduce a PDF under 100KB?
Compress it, then if needed lower image resolution or convert scans to grayscale — images are what make PDFs large.
Why is my PDF so large?
High-resolution images and scans. Text adds almost nothing; a scanned page can be several MB.
Can I hit an exact size like 100KB?
Not to the byte, but you can get under a target by using stronger compression and lower image quality, then checking.