How to compress a PDF to under 2 MB

There are two kinds of heavy PDF, and they need opposite fixes.

A text PDF comes from Word or Google Docs. It is naturally light — rarely over 1 MB even with dozens of pages. If one is heavy, the culprit is usually an embedded font or a very high-resolution image inside it.

An image PDF comes from a scanner or a phone photo. Each page is a photograph, and a 12-megapixel photo alone is 4–6 MB. Five scanned pages easily make a 25 MB file. This is the case almost every time someone needs to compress.

For image PDFs, the gain comes from lowering resolution and recompressing pages. On-screen reading needs no more than 150 DPI; ordinary printing is fine at 200. Going from 600 DPI to 150 cuts the file by about 90%.

Scanning in black and white or greyscale, when nothing relevant is coloured, cuts more. An ID scanned in colour at 600 DPI can be 8 MB; the same document in greyscale at 200 DPI is 400 KB and just as readable.

For text PDFs there is little to compress — reprocessing one usually increases the size, because it turns vector text into images.

• Split the document. Many forms accept several attachments.
• Remove unnecessary pages — cover sheets, blank backs, instruction pages.
• Rescan with the right settings instead of compressing a bad scan.

What does not work: renaming the extension or zipping it. PDF is already compressed; a zip saves about 2% and may be rejected.

The documents that most need compressing are the most sensitive ones — IDs, contracts, payslips. Most online compressors upload your file to a third-party server, where it sits for hours.

The Localside PDF compressor runs entirely in your browser: the file never leaves your device. It tries several strategies and returns the smallest one — and if none beats the original, it tells you the file is already optimised instead of handing back something worse.