Online application forms love small numbers. "Upload your certificate as a PDF, maximum 200 KB." "Signature and photo under 100 KB." "Supporting documents, each no larger than 500 KB." A photo from a modern phone is 3 to 5 MB on its own, so the gap between what you have and what the form accepts can be fifty times or more.
It can almost always be closed, but not by pressing a compress button harder and harder. The order you do things in matters more than any single setting. This guide covers what is realistic for each limit and the sequence that gets there with the least damage.
What each limit can realistically hold
It helps to know roughly what fits before you start, so you do not chase the impossible.
- Typed documents (a CV or letter exported from Word) are tiny: usually 30 to 150 KB for several pages. If one of these is over the limit, something unusual is inside it, often a large logo or a pasted photo.
- One scanned page fits comfortably under 200 KB in greyscale at 150 DPI, and under 100 KB at 100 to 120 DPI. Colour roughly doubles it.
- A multi-page scan under 200 KB is hard. Plan on about 50 to 70 KB per greyscale page at a readable resolution, so a 3-page certificate is near the limit and a 10-page one will not fit without becoming hard to read.
- 500 KB is generous for anything except long colour scans.
If the maths says it cannot fit, the answer is usually fewer pages rather than more compression. Many forms only need the page with the result or the seal on it.
The order that works
- Remove pages that are not needed. A blank back side, a cover sheet, terms and conditions nobody asked for. Each page you drop saves its whole weight. Use Delete pages.
- Crop away borders. A dark scanner edge or a strip of table around a phone photo is detail the compressor has to keep. Crop PDF with auto-crop trims each page to its printed area.
- Convert to greyscale if colour is not required. Certificates, mark sheets and ID copies are almost always acceptable in greyscale, and it roughly halves the size of a scan. Use Greyscale PDF, or tick greyscale in the compressor.
- Compress last, once, aiming at the actual limit. In Compress PDF, start with a medium setting and only go stronger if the result is still too big.
Doing this the other way round, compressing first and then trimming, wastes quality: each compression pass throws information away, and doing it twice loses more than doing it once at the right strength.
Choosing the resolution
Resolution is the most powerful lever. Halving the DPI cuts the pixels to a quarter. For a document that will be read on screen by an officer, 150 DPI is clear and 120 DPI is usually fine. Below 100 DPI small print, such as the fine text on a certificate or the numbers in a seal, starts to blur. Zoom into the preview and read the smallest text on the page before you upload: if you cannot read it, the person checking it cannot either.
If it is still too big
- Rescan instead of recompressing. A phone photo taken in bad light is full of noise, and noise does not compress. Rescan in daylight, flat, filling the frame. See how to scan properly with a phone.
- Split the upload if the form allows several files.
- Check whether a typed version exists. A certificate downloaded from the issuer's website is a fraction of the size of a scan of the printed copy.
Mistakes that get uploads rejected
Some portals reject files that pass the size limit, for other reasons:
- The file is a renamed image (photo.jpg renamed to photo.pdf). Convert it properly with JPG to PDF.
- The PDF is password protected. Portals cannot open it.
- The page is sideways. Fix it with Rotate PDF before compressing.
- The file name has unusual characters. Stick to letters, numbers and hyphens: Sharma-SLC-certificate.pdf.
For the wider picture of why portals set these limits and how page size checks work, read Getting a document past a government portal upload limit.