Can a PDF really go under 20 KB?
Sometimes. It depends on what’s inside the file, not on which website you use.
A PDF typed in Word or Google Docs and saved as PDF, with no photos, is mostly text plus the fonts to draw it. That’s light, and a one-page letter made that way is often close to 20 KB already. We pack its structure tighter and there’s a fair chance it fits. We never change the text or its fonts, so if it doesn’t fit after that, the rest is up to how the file was made.
A scan or a phone photo of a page is a different thing. It’s a picture, and a picture of a page has a floor. In the tests above, the smallest readable versions of a one-page certificate came out at 29 KB from a phone photo and 32 KB from a scanner, at about 60 DPI. That’s the point where letters still read, with rough edges. Going lower turns the page into blocks you can’t read, and a form that accepts an unreadable document hasn’t really accepted it.
So if your file is a scan, this page will try, then give you the smallest readable version and tell you plainly that it’s still above 20 KB. You won’t get a file that only looks like it passed.
Check what the form is actually asking for
Limits this small are common on exam and recruitment forms, usually for the photo or the signature. Those boxes almost always want a JPG, not a PDF. If the upload says “JPG/JPEG, 10 to 20 KB”, you’re in the wrong tool: a PDF won’t be accepted however small it is.
If it really is a PDF the form wants, read the label again for the number of pages. “Upload page 1 of your mark sheet” means one page, and one page is far easier to fit than four.
What to try when a scan won’t fit
- Send only the page they need. Extract PDF pages lets you tap the one page and save it on its own. Then compress that.
- Crop before you make the PDF. A phone photo that shows the desk around the paper spends bytes on the desk. Crop the photo to the edges of the paper in your Photos app, then use JPG to PDF and come back here.
- Use the original digital file if there is one. Certificates and statements downloaded from the issuing website, or from DigiLocker, are usually made of real text rather than a photo. Those can go far lower than a scan of a printout.
- Rescan in black-and-white mode. Scanners and scanning apps have a black-and-white (not greyscale) setting meant for typed pages. It makes much smaller files than colour.
If the file has several pages
When the form lets you upload more than one file, Split PDF by size can cut a text PDF into parts that each stay under the limit, numbered so nothing gets lost. That won’t help a single scanned page: one page can’t be split.
For anything with a bit more room, the 50 KB page fits one scanned page while it stays readable.
Checked against the tool on 22 October 2026. How we write and test these guides