How do you reduce a PDF's size so a portal will accept it?
By the PdfDady team · Updated · 8 min read
If a portal says "file size exceeds the limit", the cause is almost always the pictures inside your PDF, not the text. Scanned pages and phone photos are images, and images are heavy. Shrink those and the file shrinks. Typed text weighs next to nothing.
So the fix depends on what your PDF is made of. A PDF with real text and a few photos can be made smaller without touching the text. A PDF that is all scans has to give up some sharpness. You can do either with our Compress PDF tool, which runs in your browser, so the file is not uploaded anywhere while you work on it.
First, find the real limit
Read the upload instructions before you compress anything. Limits differ a lot from one portal to the next, and sometimes from one field to the next on the same form. Three things to look for:
- The maximum size, and whether it is per file or for all files together.
- A minimum size, if there is one. Some forms reject files that are too small as well.
- The format. A field that wants a PDF will not take a JPG, however small.
To give one verified example: the Income Tax Department's e-Proceedings help page says a single attachment can be at most 5 MB, you can add up to 10 attachments, and all of them together cannot exceed 50 MB. Your exam form, bank or university portal will have its own numbers. Don't trust a figure you read on a blog (including this one) for your portal. Check the portal's instructions or the application notice.
Then check your file. On a phone, long-press the file in your Files app and open its details. On a computer, right-click and choose Properties (Windows) or Get Info (Mac).
Why your PDF is so big
A page of typed text is tiny as data. A photo of the same page is not. A single photo from a phone camera is often several MB, and a PDF made from five such photos is roughly five photos in size.
The usual causes, heaviest first:
- Phone photos turned into a PDF at full resolution. The camera captures far more pixels than a document needs.
- Colour scans. Colour takes more data than grey, and grey more than pure black and white.
- High scanner settings. A page scanned at 600 DPI has four times the pixels of the same page at 300 DPI.
- Many pages. Twenty modest scans still add up.
A PDF exported straight from Word, Google Docs or a billing system is usually small already, because it stores letters and fonts rather than pictures of them. If a file like that is large, it has big images placed in it.
How to reduce the size, step by step
- Open Compress PDF and add your file. One PDF at a time, up to 100 MB.
- Leave the mode on Keep text for the first try. It re-compresses the photos and scans inside the PDF and leaves text, links, bookmarks and form fields alone.
- Choose Balanced or Strong. Balanced limits images to 2000 pixels on the long edge at JPEG quality 75%. Strong goes down to 1400 pixels at 60%, which saves more and shows more in photos.
- Press Compress PDF. The tool shows the original size and the new size.
- If the result is still over your limit, switch to Smallest size, pick a target (100 KB, 200 KB, 500 KB, 1 MB, or your own figure from 20 KB to 50 MB) and compress again.
- Download
compressed.pdf, open it and read every page before you upload it.
That last step matters. A file that fits the limit and cannot be read will be rejected by a person later instead of by the portal now, which is worse.
Keep text or Smallest size: which one
| Keep text | Smallest size | |
|---|---|---|
| What it does | Re-saves the images inside the PDF as smaller JPEGs | Turns every page into one JPEG image |
| Text | Stays selectable and searchable | Becomes part of the picture; cannot be selected, searched or copied |
| Links and form fields | Keep working | Stop working |
| Can aim for a KB target | No | Yes, for PDFs up to 100 pages |
| Best for | Reports, statements and forms with some photos | Scans, and any file that must get under a strict limit |
Start with Keep text when the limit is generous (a few MB) and the file has real text. You lose nothing you would notice on a text page.
Go to Smallest size when the limit is tight or the file is all scans. With a target set, the tool tries several resolutions (150, 120, 100, 80 and 60 DPI) and several quality levels, and keeps the sharpest version that fits. If nothing fits, you still get the smallest version it could make, with a note that it is over the target.
One detail that helps with strict portals: the tool counts 1 KB as 1,000 bytes. A file it reports as under 200 KB is therefore also under 200 KB for a site that counts 1,024 bytes to the KB.
When compression is not enough
Sometimes the target is simply too small for the number of pages. A few honest options:
Upload fewer pages. If the form wants only the marksheet, don't send the whole booklet. Save just the pages you need with Extract PDF pages, then compress that.
Rescan with lower settings. If you still have the paper, scanning again is often better than squeezing a heavy scan. The Income Tax Department's own advice for attachments is to scan to PDF at 300 DPI, in black and white only. A black-and-white document scan is far lighter than a colour photo of the same page.
Split it, if the portal allows several files. Some portals accept multiple attachments with a per-file limit. Check the instructions first, since many fields take exactly one file.
Don't expect grayscale to fix size. Converting a PDF to grey with Grayscale PDF is the right move when a submission must be black and white, or to save colour ink. It redraws every page as an image, so the file can come out larger or smaller. If size is the goal, compress after converting.
For very small targets, see our guide on getting a PDF under 100 KB, which goes through what is realistic by page count.
Common problems
"There is no download after compressing." The result was not smaller than the original, so the tool does not offer it. This happens with PDFs that are mostly text, or already well compressed. Try Smallest size if you can live without selectable text.
"Keep text barely changed anything." That mode only touches photos and scans. A text-only PDF has nothing for it to shrink. A few image types, such as CMYK or masked images, are also left as they are.
"The tool refused my file." Password-protected and encrypted PDFs are refused in both modes. If you know the password, save a password-free copy first with Unlock PDF, then compress. Keep in mind that some portals also reject protected files. The Income Tax guidance, for one, says not to upload files with read, write or password protection.
"The portal still rejects it." Check the format the field accepts, any minimum size, and the file name. Some portals dislike spaces or special characters in names. If the error message is vague, the portal's help page or helpdesk is the only reliable answer.
Questions people ask
Will compressing reduce the quality?
In Keep text, text is untouched and photos lose a little detail. In Smallest size, the whole page is saved as a lower-resolution image, so everything softens somewhat. How much depends on how far the file has to shrink.
How much smaller will my PDF get?
Nobody can promise a figure, because it depends on what is inside. Scans and photos shrink the most. A PDF that is mostly text may hardly change. The tool shows both sizes before you download, so you find out in a few seconds.
Can I compress a PDF on my phone?
Yes. The tool works in a phone browser, and the file stays on the phone.
Is it safe to compress an Aadhaar or bank statement this way?
The compression happens in your browser and the PDF is not uploaded, so the document does not leave your device during the process. What you do with the compressed copy afterwards is the part to be careful about.