You try to attach a PDF and the email bounces, or an application portal says the file is too large. Gmail, for example, caps attachments at 25 MB, and many portals allow far less. The good news: most oversized PDFs can be shrunk dramatically.
Why is my PDF so big?
PDF size depends almost entirely on what is inside:
- Scans and phone photos. Each page is a full-resolution image, often 2–5 MB per page.
- High-resolution images placed into a document, such as photos in a brochure.
- Embedded fonts add a little, but rarely cause a real problem.
A 20-page contract exported from Word is usually under 1 MB. The same contract scanned on a phone can be 50 MB.
Method 1: Compress the PDF
Open Compress PDF, drop the file and choose a level:
- Recommended works for most documents and stays readable on screen.
- Strong gives the smallest file, good for email when quality matters less.
- Light keeps more detail if the document will be printed.
The tool re-saves each page as an optimised image. That is why it works so well on scans. The trade-off is that text becomes part of the image and can no longer be selected. If the result is not smaller, you get your original back.
Method 2: Send only the pages you need
Often the recipient does not need all 40 pages. Use Split PDF with a custom range such as 1-3, 10 to keep just the pages that matter.
Method 3: Fix it at the source
- Scanning on a phone? Use a lower resolution or a "document" mode, which saves black-and-white pages that are much lighter.
- Building a PDF from photos? Shrink the photos first, then combine them with JPG to PDF.
- Exporting from Word? Choose the "Minimize size (publishing online)" option when saving as PDF.
- On a Mac? Preview offers File → Export → Quartz Filter → Reduce File Size, which is aggressive but quick.
When compression does not help
If your PDF is mostly text and already small, compression has little to remove. In that case, split the document, or share it as a link through cloud storage instead of attaching it.