How to get a PDF under the email size limit
· 5 minute read
A PDF too big to attach? What makes it large, what to try before compressing, and how to hit a size limit without making the document look worse.
The attachment limit for most email systems is about 20 to 25 megabytes, and application portals are often stricter. A scanned document or a brochure can easily be over that. The message "file too large" arrives at the worst moment, usually just before a deadline. The good news is that a PDF is nearly always bigger than it needs to be.
Find out why it is big
Text is tiny. A page of text takes only a few kilobytes. A file measured in megabytes is almost always large because of pictures: a scan, which is a photograph of every page, or a document with high-resolution images placed in it. If your file is 30 MB and 10 pages long, the pictures are the problem.
Things to try before compressing
- Send only the pages that are needed. Pull them out with Split PDF.
- If the file is a scan, rescan at 150 to 200 dots per inch in greyscale. This is plenty for reading, and far smaller than 600 dots per inch in colour.
- If the PDF was made from photographs, shrink the photographs before you convert them. A phone photo is usually many times larger than a page needs.
- Check for duplicates. A merged file can contain the same attachment twice.
Compressing without wrecking it
Compression works by re-encoding the pictures at lower quality or smaller dimensions. The words, drawings and fonts do not need touching, and a good tool leaves them as they are, so the text stays sharp. There are usually levels. Use the lightest one that gets you under the limit.
Always compress from the original. Compressing a compressed file loses quality twice, and the second loss buys very little.
Check the result
Open the compressed file and look at the pages with photographs, stamps and signatures, since those are where quality loss shows first. Look at small print as well. If anything is too soft, go back to the original with a lighter setting.
When compression does nothing
If the file is mostly text, it is already small, and a compressor has nothing to work with. A good tool tells you so and gives you your original back, rather than handing you a file that is no smaller. At that point the options are to split the file into parts, or to share a link to it, rather than attach it.
Mind where it goes
Some compressors upload your file and keep it for a while. For a personal or confidential document, prefer one that works in the browser, so the file stays on your computer. Reduce PDF file size explains how compression works in more detail.
Tools mentioned
- Compress PDF — A smaller file that still reads like the original.
- Split PDF — Take a range of pages out into a file of their own.
- JPG to PDF — Photos and scans gathered into one document, each page its image.