PDF too large for Canvas or Blackboard? Shrink it

Updated on October 15, 2026

It’s 11:40 p.m., the deadline is at midnight and the portal rejects your report: file too large. Don’t panic. Often you can still get your PDF small enough, without installing anything and without sending your work to a stranger’s server.

Why your PDF is rejected

Canvas, Moodle, Blackboard and Google Classroom only accept files up to a certain size per upload. That limit differs per school or university, and sometimes even per assignment: your teacher or the school’s support team sets it. So first check the assignment description or the error message to see how many MB are allowed.

The weight is almost always in the images. Photos of a lab setup, scanned appendices, full-resolution screenshots, a poster you exported as a PDF: those are the heavy parts. Plain text weighs almost nothing.

How to shrink your PDF

1. Open the Compress PDF tool.
2. Drag your PDF into the box or click to choose it. You can add several files at once.
3. Choose a level: Light, Balanced or Strong. Start with Balanced.
4. Click Compress.
5. Download the result and compare the size. Check the new size against your portal’s limit.
6. Open the new PDF and scroll through it. Are charts, formulas and photos still easy to read? Only then hand it in.

Still too large? Try Strong. That gives you the smallest file, but with visible quality loss in the images. For a report with photos, that’s often fine. For a photo portfolio, usually not.

Not small enough?

If your PDF has few or no images, it barely gets smaller. You then get the original back unchanged. PDFs with images meant for print (CMYK) sometimes hardly shrink either. Three things that do help:

• Export again from the source. Did you write it in Word? When you save as PDF, choose the option for minimum size (publishing online).
• Make photos smaller before you insert them. A phone photo 4,000 pixels wide is rarely needed in a report.
• Hand in appendices separately, if the assignment allows it. With Split PDF, you take them out of your main file in a few clicks.

Does your file need to fit through an inbox rather than a portal? Read PDF too large to email? Compress or split it.

Why not upload it?

A thesis, an internship report with data about patients or clients, research that hasn’t been published yet: you don’t want that on the server of an unknown website just to make it smaller. Yet many online tools do upload your file to their server.

With PDFCommunity, compressing happens in your browser. Your files are processed on your own device and not uploaded. You don’t have to take our word for it: check it yourself in your browser’s network tab. Verify that no PDF is uploaded explains how, step by step.

Good to know

• On your phone, large files can be slow or too heavy for your device’s memory. The tool warns you beforehand if a file is too large for your device. In doubt, use a laptop.
• There’s no fixed saving. How much smaller your PDF gets depends entirely on what’s in it. Sometimes a lot, sometimes almost nothing.
• Always check the result yourself before you hand it in, especially tables, charts and small print.
• Don’t wait until the last minute. Uploading to a busy portal can be slower right at the deadline. So shrink your file a day ahead if you can.

Frequently asked questions