How to reduce PDF file size without ruining it
A PDF that is too big to email or upload is a common annoyance. The good news is that most oversized PDFs can be shrunk a lot. Which method works best depends on what is making the file large.
Why PDFs get so big
Text is tiny. A page of plain text takes only a few kilobytes. What makes PDFs large is almost always images: scanned pages, photos, screenshots and logos saved at very high resolution.
A 20-page scan from a phone or office scanner can easily reach 30 MB, even though the same 20 pages typed out would be under 1 MB. That is the file type where compression helps the most.
1. Compress the PDF
Compression redraws each page at a lower resolution and saves the images more efficiently. For scans and photo-heavy PDFs this often cuts the size by more than half with no obvious change on screen.
Start with a balanced setting and check the result. If the file is still too big, step up to a stronger setting. Keep in mind that this kind of compression turns pages into images, so the text can no longer be selected or searched.
2. Remove pages you do not need
Blank back sides, cover sheets and duplicates add weight for no benefit. Deleting them shrinks the file and makes it easier for the reader to get to the point.
3. Split a large PDF into parts
When a site limits each upload, it can be easier to split the document into two or three parts than to compress it hard. Splitting does not change quality at all, because the pages are copied as they are.
4. Shrink the images before you build the PDF
If you are making a PDF from photos, reduce them first. A phone photo is often 3 to 8 MB, far more than a page needs. Resize the images to a sensible size, or compress each one to a target such as 200 KB, and then combine them into a PDF.
5. Export again from the original app
If you still have the source document, exporting it again with a smaller-size option can beat any after-the-fact compression. In Microsoft Word, for example, saving as PDF offers a "Minimum size" option for documents that will only be read on screen.
A quick checklist before you send it
- Open the compressed file and page through it. Is small print still readable?
- If you need to keep searchable text, use the option that only repacks the file.
- Keep your original file. Compression cannot be undone.
- Check the file size against the limit of the form or email service.