Why Your PDF Won't Upload, and How to Shrink It Without Ruining It
You fill in an online application, attach the PDF, click submit, and get the message every office worker has seen: file exceeds the maximum size of 5 MB. The document is only six pages. How did it get so big?
Where the megabytes come from
Text in a PDF is tiny. A hundred pages of plain text is often under a megabyte. The weight almost always comes from images, and the worst offenders are scanned pages. When you scan a page or take a photo of it with your phone, each page becomes a full-resolution picture, frequently 3,000 pixels wide or more, saved with little compression. Six of those and you are well past any upload limit.
Other common causes:
- Embedded fonts in documents exported from design software.
- Photos pasted into a Word document at full camera resolution before exporting.
- Repeated “print to PDF” cycles that add layers without removing anything.
Pick the right goal before compressing
Ask what the file is for. A form upload or an email attachment needs to be readable on screen and maybe printable on an office printer. It does not need magazine-quality images. That gives you a lot of room to compress.
If, on the other hand, the PDF is a portfolio or contains fine diagrams, compress gently and check the result closely.
Compressing in practice
The simplest route is a browser-based tool. I use FileOtter's PDF compression page: drop the file in, choose a compression level, download the smaller copy. For a typical scanned document, a medium setting usually cuts size by well over half while keeping text sharp.
After compressing, always open the result and zoom in on the smallest text, such as a signature line or footnote. If it is still legible, you are done. If it has turned blocky, go one level lighter.
If it is still too big
Sometimes one compression pass is not enough. A few other moves help:
- Remove pages that are not required. Application portals rarely need the blank back side of every scanned page.
- Split the document. Many forms accept multiple attachments. Two 3 MB files may go through where one 6 MB file will not.
- Rescan in greyscale. Colour scans of black-and-white documents waste space. Greyscale at 150 to 200 dpi is plenty for most paperwork.
- Re-export from the source. If you created the PDF from Word or Google Docs, shrink the images there first, then export again.
Privacy worth thinking about
Documents that need uploading are often sensitive: tax forms, ID scans, medical letters. Before using any online tool, read how it handles files. Prefer tools that state they delete uploads quickly or process files in the browser, and avoid uploading identity documents to random sites you found five minutes ago.
A habit that prevents the problem
Set your phone's scanning app to a reasonable resolution once, and you will rarely hit an upload limit again. In most scanner apps there is a quality or size option hidden in settings. "Medium" or "standard" is almost always enough for paperwork.
Quick reference
For email: aim for under 10 MB, ideally under 5. For government and job portals: check the stated limit, which is often 2 to 5 MB per file. For printing: compress lightly and test print one page. Most of the time, a single compression pass and a quick zoom check is all it takes.