Guide · PDF tips
How to reduce PDF size for email and upload
Updated 12 October 2026 · 6 minute read
A PDF that is too large will bounce from an email, fail to upload to a portal, or take forever on a slow connection. You can almost always make it smaller without losing what matters. This guide explains what makes a PDF big, how our compression levels differ, and what to do when compression alone is not enough.
Why PDFs get large
Text is tiny. A hundred pages of plain text is only a few hundred kilobytes. Large files almost always come from images: scans, photographs, screenshots or high-resolution pictures pasted into a document. A scanned page, for example, is a full-page photo, which is why scanned documents are far bigger than typed ones.
Try the lightest option first
Open the Compress PDF tool and choose your file. You get four levels, from gentle to strong:
- Basic cleans up the internal structure without touching the pictures. It is lossless and keeps text selectable, but savings are usually small.
- Recommended rebuilds each page as an image at about 120 dpi. It balances quality and size, and suits most documents.
- Strong uses about 90 dpi for a noticeably smaller file, with some loss of fine detail.
- Extreme uses about 60 dpi for the smallest file. Text is readable on screen, but small print becomes soft.
Start with Basic. If the file is still too large, move up one level at a time, and stop as soon as it fits.
What you give up
Every level except Basic turns each page into an image. Two things follow from that:
- Text is no longer selectable or searchable. If you need that, run the compressed file through OCR PDF afterwards.
- Fine detail softens. This is fine for reading on a screen, but barcodes or tiny print may suffer. Do not compress a shipping label you intend to print and scan.
See the result before you send
When compression finishes, the tool shows the size before and after, for example “4.2 MB → 1.1 MB (74% smaller)”. Open the downloaded file and check that the pages are readable. If the tool says the file is already as small as it can get, the PDF was already well optimised, and a stronger level is the next step.
When compression is not enough
If a file is still too large for an upload limit, shrink the amount of content instead:
- Remove pages that you do not need, such as blank pages or covers.
- Split the PDF into two or three parts and send them separately.
- If the document came from photos, rebuild it with JPG to PDF after resizing the pictures, so each page is not a huge camera image.
- Use PDF to JPG at a lower quality if you only need pictures of pages.
A simple decision guide
- Typed document with images: try Basic, then Recommended.
- Scanned document: go straight to Recommended or Strong, then OCR it if you need text.
- Still too big: remove pages or split the file.
- Needs perfect quality (printing, legal or label files): do not compress. Split it instead.
Your files stay private
Compression runs inside your browser. The PDF is not uploaded to a server, so you can shrink contracts, ID copies or invoices without sending them to a third party. Closing the tab discards the file.
Frequently asked questions
Why did my PDF not get smaller?
It may already be well optimised. Basic compression only cleans up the file structure, so try Recommended or Strong, which rebuild the pages as compressed images.
Does compression reduce quality?
Basic compression is lossless. Recommended, Strong and Extreme lower the image resolution, so very fine detail becomes softer.
Can I still select text after compressing?
After Basic compression yes. After the stronger levels the pages become images, so use OCR PDF afterwards if you need searchable text.