Guide
PDF compression is a decision about the receiving site's limit, the document's structure, and what must remain readable. These guides explain those decisions before you change the file.
Copy the exact maximum size from the form before compressing. A 1 MB limit, a 1,000 KB limit, and a vague 'file too large' message are not the same instruction. When the form gives a number, aim slightly below it so rounding and metadata differences do not put the download back over the boundary.
A scan is mostly page images; an exported document is usually text, fonts, vectors, and a smaller number of images. Scans often have more removable image data. Text PDFs may already be efficient, and forcing them through image compression can trade away search, selection, links, and accessibility for only a modest size reduction.
PDF Limit first attempts a text-preserving rewrite. Balanced and strong modes can rebuild pages as compressed images when a stricter target needs a larger reduction. Start with the gentler result, inspect it, and only accept rasterization when the upload requirement matters more than selectable document structure.
Passing the byte limit does not prove that a signature is legible, a barcode scans, a form field still works, or every page is present. Open the downloaded PDF, move through the full page count, zoom into fine text, and verify the exact file in the destination portal.
If a result stays over target, learn which part of the file is expensive before trying again. Removing unused pages, exporting source images at sensible dimensions, or starting from the original document can produce a better result than repeatedly recompressing an already degraded PDF.