The short answer
UPSC allows up to 500 KB per PDF certificate at the DAF stage. Not 50 KB. Not 100 KB.
If you have been trying to force a scanned degree certificate down to 50 KB because a website told you to, stop — you are destroying quality you were never required to give up. Set the target above to 500 KB and your document will come out clearly readable.
The limits, as UPSC actually states them
| Upload | Format | Size |
|---|---|---|
| DAF certificates | up to 500 KB each | |
| Photograph | JPG | 20–300 KB, 350×350 to 1000×1000 px, white background |
| Signature | JPG | 20–300 KB, handwritten, black ink, white background |
⚠️ Check the notification for your specific exam before you submit. UPSC changes these between exams and between stages, and the Commission's own notification is the only authority. Anything on this page — or any other — is a summary, not the rule.
Why almost every page about this is wrong
Search for "compress PDF for UPSC" and nearly everything says 20 KB, 50 KB or 100 KB. Those numbers are real, but they belong to the photograph and signature, which are JPG images uploaded separately from your documents.
Somewhere along the way the image limit got attached to the PDF requirement, and every site since has copied it. The result is thousands of candidates compressing certificates ten times harder than necessary and submitting scans the Commission struggles to read.
500 KB is a generous limit. A one or two page certificate at 500 KB is roughly 250 KB per page — comfortably above the point where scanned text begins to degrade. You should see no visible loss at all.
Why your scan looked terrible at 50 KB
If you already tried and the result was unreadable, this is why.
A scanned certificate is not text. It is a photograph of text — the letters are just dark pixels. How readable it stays depends entirely on how many pixels survive.
Most compressors handle this by rendering each page and saving it as a JPEG. JPEG was designed for photographs, where colours blend smoothly. Black text on white paper is the opposite — hard edges everywhere — so JPEG smears a grey halo around every letter. Squeezed hard enough, the letters merge.
At 50 KB for a full page, there is simply not enough information left to form readable characters. No tool avoids that, because it is arithmetic rather than software.
This tool handles scans differently: it converts the page to sharp black-and-white at a higher resolution instead of blurry grey at a lower one. On a real four-page scanned report that produced a 70 KB file that was still readable, where the usual approach needed 111 KB and was not. But even so — at 500 KB you do not need any of that cleverness. You have room to spare.
What to do, step by step
- Scan or photograph the certificate. Flat, even light, camera directly overhead, filling the frame. A phone photo taken at an angle is much harder to read once compressed.
- If it is an image, convert it first with images to PDF. Nothing is re-encoded, so no quality is lost on the way in.
- Compress to 500 KB using the tool above — not lower.
- Open the result and read it. Every line. If you cannot read a date or a seal, the Commission cannot either.
- Keep the original. Always.
If 500 KB still is not enough
Occasionally a multi-page document with colour scans genuinely will not fit. In that case:
- Rescan in black-and-white at 200 DPI. This is the single most effective fix. A scanner discards the paper's cream tint, the shadow from the binding and the sensor noise — none of which carry information, all of which consume file size. The same document rescanned properly will often be a quarter of the size and more readable.
- Split the document if the portal accepts certificates separately. Extract just the pages you need rather than compressing everything harder.
- Do not go below roughly 100 KB per page on a scan. Below that, readability falls away quickly whatever tool you use.
The photograph and signature are a different problem
A PDF compressor cannot help with those. They are JPG images with pixel-dimension rules as well as size rules — minimum 350×350, maximum 1000×1000 — so you need to control resolution and file size together.
Get them wrong and the application is rejected at upload, before anyone reads it. Follow UPSC's specification exactly: white background, black ink for the signature, and the exact dimensions in the notification for your exam.
Sources
Neither replaces the official notification for your exam. Read that.