Compress PDF to 20MB

Twenty megabytes is a lot of document. A hundred colour pages, a hundred and fifty greyscale ones, or five hundred pages of text. Files that pass it are usually carrying something beyond their page count: embedded attachments, a full set of unsubsetted fonts, the same image stored once per page, or scans made at a resolution nobody chose deliberately.

Where the 20 MB limit comes from

Twenty megabytes is the practical ceiling for anything that travels as an attachment, which is why it recurs across mail systems and any portal whose back end eventually mails the file to somebody. If the 20 MB you are aiming at is specifically an email attachment, compressing a PDF for email covers the part this page does not: encoding overhead means a 20 MB file does not arrive as a 20 MB attachment.

How the tool hits 20 MB

What fits in 20 MB, and what does not

Page count alone rarely explains a file of this size. Text costs about forty kilobytes a page and colour scanning about two hundred and forty, so five hundred text pages and eighty colour pages weigh roughly the same. When the arithmetic does not account for the file in front of you, the extra weight is structural.

When it cannot reach 20 MB

Some documents will not fit legibly, and the tool says so rather than pretending. When the result line reports a miss, three moves usually solve it:

• Split first. Use Split PDF to break the file into parts and compress each. Most portals accept several attachments even when each one is capped at 20 MB.
• Rescan the source. A fresh 150 dpi greyscale scan compresses far better than a colour scan that has already been through one compressor. Every pass costs quality, and the first pass should start from the cleanest source.
• Check the real limit. Portals sometimes state one number and accept another. Read the fine print, or try a slightly larger file before compressing harder than you need to.

The result line tells you what was heavy

When the tool finishes it prints one sentence naming the stage that produced the file you are downloading. It is easy to skim past and it is the most useful thing on the page, because each of the three stages attacks a different kind of weight. Knowing which one succeeded tells you what your document is actually made of.

A file that reaches the cap at stage one was carrying dead weight. Editors leave behind page thumbnails, private application data and old metadata, and on a large document that can run to megabytes with nothing visible attached to it. Nothing about the document changed and nothing needs checking.

Stage two is the ordinary case. The pictures came down to a stated resolution and everything else was left alone. The number in the message is worth reading: 200 or 150 ppi means the images were barely touched, while 72 or 60 means they were already marginal and the document is worth a look before it goes anywhere important.

Stage three is the interesting one. It means the images were not where the weight was, which leaves a short list: heavy vector artwork such as a map or a CAD drawing, a full set of embedded fonts that were never subsetted, or files attached inside the PDF. That last case deserves saying plainly, because this tool will not touch it: embedded attachments are not removed. Silently deleting part of a document is not compression, and a contract that loses its attached spreadsheet on the way to a size cap has been damaged rather than shrunk. If you suspect attachments, open the file's attachments panel in a reader and decide for yourself.

Where people use the 20 MB target

Why this runs in your browser

A twenty megabyte PDF is usually a complete bundle: a bid, a return, a case file, an archive. Uploading one to a compression service means sending the whole bundle to somebody with no reason to have it, and waiting on a slow connection while it goes.