How to Reduce a PDF's Size When a Portal Rejects It
Why PDFs get large, and practical ways to shrink one below a college or exam portal's upload limit without making it unreadable.
Why PDFs get so big
A PDF made from typed text is usually small. Large PDFs are almost always full of images: phone photos of handwritten pages, scanned certificates, or screenshots. A single 12-megapixel photo can add several megabytes on its own, so a ten-page scan can easily pass the limit on a portal.
Start with the cause
Before compressing, ask where the size comes from. If you scanned pages at very high resolution, rescanning at a lower setting may help far more than compressing afterwards. If the file contains a few large photos, resizing those images before you build the PDF is better than squeezing the whole document.
Compress the file
Use a compression tool and check the result. Compression lowers the quality of the images inside the PDF, so open the output and make sure text, stamps and signatures are still clearly readable. If the file is still too large, try again with a stronger setting, but stop before small text becomes blurry.
Split instead of squeezing
Some portals allow several uploads, such as one file per document. In that case, splitting a large PDF into logical parts, for example the report and the annexures, can be easier than forcing everything into one small file. Check the portal's rules first.
Merge only what you need
If you are combining files, remove pages that are not needed before merging, such as blank pages or duplicate scans. Fewer pages means a smaller result before any compression.
Know where your file goes
Tools that run in your browser keep the file on your device. Tools that compress on a server upload the file temporarily. For documents with personal details, such as ID proofs, prefer the tool that processes locally where one exists, and read the tool's privacy note.
This guide is general information. Rules differ between institutions, so confirm requirements with your college or the portal you are using.