Compress PDF to 800 KB

Most limits you meet are round numbers, 500 KB, 1 MB, 2 MB, and 800 KB is rarely the rule itself. It is the answer to two situations. The first is a total budget: an application portal that allows, say, 4 MB across five attachments, or a mailbox that bounces anything over a few megabytes, divides neatly into 800 KB per document. The second is headroom under a 1 MB field when the file may still grow, for example after you add a signature or the portal adds a cover sheet.

Both cases are common in rental applications, insurance claims and job portals, where pay slips, bank statements, ID scans and reference letters go up together. A phone scanner app typically saves each page at several hundred KB in color, so a five-page bundle easily reaches 3 MB before compression.

Most of a scanned PDF's weight is images, so that is where the tool works first: it re-encodes page images as JPEG and lowers their resolution only when quality alone is not enough. Lowest image quality sets the floor; below it the tool reduces resolution rather than letting letters break into blocks. Subset fonts and Remove metadata trim the rest, and PDF 1.5 object streams, part of the format since 2003 and of ISO 32000-1 since 2008, pack the file's internal structure tighter.

Built-in options are blunter. The Reduce File Size filter in macOS Preview often drops images to a resolution that makes small print fuzzy, with no target to aim at. If your document starts as photos rather than a PDF, image to PDF under 1 MB builds it at a controlled size, and our guide to scanning documents to PDF shows how to scan smaller in the first place.