Gmail lets you attach up to 25 MB, and Outlook about 20 MB. Many upload forms allow far less. If your PDF is too big, compressing it is usually faster than splitting it or sending a download link.
Why are some PDFs so large?
Almost always, it's images. Scanned pages, photos and screenshots stored at high resolution make up most of a large PDF's size. Embedded fonts and leftover editing data add a little more. That's why compression mostly works by shrinking images.
Method 1: Compress with PDFJig
- Open PDFJig's Compress PDF tool and choose your file.
- Pick a level: Strong for most files, Smallest for on-screen reading, or Lossless when nothing may change.
- Click Run and download the smaller PDF.
Strong and Smallest shrink images while keeping text sharp and selectable, so the PDF stays searchable. If a level can't beat the original size, PDFJig tells you and keeps the original.
Method 2: Preview on a Mac
- Open the PDF in Preview.
- Choose File, then Export.
- Set Quartz Filter to Reduce File Size and save under a new name.
Preview's filter can shrink images aggressively, so photos may turn blurry. Check the result before you send it.
Method 3: Save a smaller PDF from Word
If the PDF came from a Word document, re-save it from Word instead. On Windows, choose File, Save As, pick PDF, and select Minimum size (publishing online). Compressing large images inside the document before saving helps even more.
Method 4: Adobe Acrobat
If you have Adobe Acrobat Pro, the Reduce File Size and Optimize PDF options give fine control over image settings. Acrobat Pro is a paid subscription.
Still too big?
- Try the next stronger compression level.
- Split the PDF into two files with a PDF splitter and send them separately.
- Remove pages nobody needs before compressing.
- For very large files, share a link from Google Drive, OneDrive or Dropbox instead of attaching.
Frequently asked questions
Does compressing a PDF reduce quality?
Lossless compression doesn't. Stronger levels lower image resolution, which is usually invisible on screen but can matter when printing photos.
Why didn't my PDF get smaller?
Text-only PDFs are already compact, so there's little to remove. Compression saves the most on scans and image-heavy files.
How small does a PDF need to be for email?
Under 25 MB for Gmail and about 20 MB for Outlook. Many forms and portals ask for 2–10 MB, so check the limit where you're sending it.