Why Your PDF Is So Large, and How to Make It Smaller
A ten-page report that weighs 40 MB is almost always carrying more than it seems. Understanding where the weight comes from helps you decide what to do about it.
What makes a PDF heavy
- Scanned pages. Each page of a scan is a full picture, so a scanned document can be far larger than a typed one.
- Large photos. A phone photo pasted into a document usually keeps its full size, even when shown small.
- Embedded fonts. PDFs carry their fonts so that they look the same everywhere. Fancy fonts can add a lot.
- Hidden data. Editing history, old objects and extra details can pile up over time.
Know your limit
Many email services cap attachments at around 20 to 25 MB, and some workplaces set lower limits. Attachments also grow by about a third while travelling through email, so a 20 MB file can act like a 27 MB one. Aim well below the stated limit.
Two ways to shrink a PDF
The gentle way removes hidden data and tidies how the file is stored. Text remains selectable and pages look identical, but savings can be small.
The strong way turns each page into a compressed picture. This can shrink scans and photo-heavy files dramatically. But text is no longer selectable or searchable, and screen readers used by people with sight loss can no longer read it.
Slimfile's Compress PDF tries the gentle way first, and tells you if it had to use the strong way.
When not to use the strong way
Avoid image-only compression on forms that must be filled in, on documents that people need to search, and on material that must stay accessible. Filled-in fields and links will not survive it either. Choose a larger target, or split the file instead.
Other options
If a file remains too large, you could split it into parts and send them in separate emails. You could also remove pages that nobody needs. For very large files, a link from a cloud storage service often works better than an attachment.
And if you control the original document, compress the images before you export the PDF. That usually gives the cleanest result of all, with text left intact.