Compress PDF to 100KB

Why 100 KB, and why it is so tight

A 100 KB ceiling is standard across SSC, UPSC, IBPS, state PSC and passport portals. It exists because these systems accept millions of uploads in short windows, and a hard cap is the cheapest way to keep them standing. The number is enforced strictly: 102 KB is rejected the same as 10 MB.

It is also small enough that whether you can reach it depends almost entirely on what your PDF is made of. A PDF exported from Word stores text as drawing instructions and is usually under 100 KB before you touch it. A PDF made from phone photos of paper stores a full photograph per page, and a single page can start at 3-5 MB.

What actually reduces the size

Compression works down a ladder, and each rung costs a little more visible quality than the last. This tool stops at the first rung that meets your target rather than squeezing as hard as it can.

• Lossless re-save - strips metadata and packs the file structure tightly. Costs nothing visually and is often enough on a text PDF.
• Resolution reduction - a 300 DPI scan carries far more detail than a form checker needs. Dropping to 120-150 DPI typically removes 60-80% of the weight.
• Grayscale conversion - removes two of three colour channels. Usually another 20-30% on a black-ink document, and often the difference between just over and just under the cap.
• Page removal - a blank reverse side from a double-sided scan still costs space, and so does a cover page nobody asked for.

When 100 KB genuinely cannot be reached

Some documents cannot hit 100 KB and stay readable. A twelve-page colour scan is one of them: there is simply too much information on the pages. When that happens you get the smallest file we managed, and the result panel states the size actually reached rather than implying success.

The better fixes at that point are upstream. Upload only the pages the portal asked for. Rescan the original in grayscale at 150 DPI instead of compressing a large colour photo after the fact - starting smaller always beats shrinking later. If the portal accepts multiple attachments, split the document rather than destroying one.

What you should not do is push until the text stops being legible. A rejected upload costs five minutes. An unreadable document attached to an application can cost the application.

Check the result before you upload it

Open the compressed file and look at the smallest text on the busiest page, plus your signature if the form carries one. Signatures suffer first under aggressive compression because they are fine detail in a small area.

Keep the original. Compression is one-way: detail that has been discarded cannot be restored by re-saving at higher quality, and portals sometimes come back asking for a clearer copy.