How to Compress a PDF to 100 KB or Less (Free, Step by Step)

"File must be less than 100 KB." Few upload limits cause more frustration, especially when your scanned document is 4 MB. Here's the exact method to get any PDF under 100 KB while keeping it readable.

The fastest path

Run your file through the compress PDF tool first — it rebuilds the PDF with optimized structure, entirely in your browser, so sensitive documents are never uploaded. For many text PDFs, one pass is enough.

If it's a scanned document

Scans are large because each page is a photo. The real fix happens before compression: rescan at 150–200 DPI instead of 600, and in grayscale rather than colour if the form allows. Resolution at scan time matters more than anything done afterward.

The 100 KB pipeline

1) If it's images, compress them first with the image compressor. 2) Convert to PDF with JPG to PDF if needed. 3) Run compress PDF. 4) Still over? Compress once more or drop the image quality — at form display sizes, you won't see the difference.

What not to do

Don't screenshot the PDF (adds loss and often increases size), and don't recompress the same file five times across random sites — each pass degrades quality. Keep your original untouched so you can redo the pipeline when the next portal demands 50 KB.

Check the page count

Fewer pages means smaller files. If you only need certain pages, extract them with split PDF first — the page counter shows what you're working with.