When 500 KB is the target
A 500 KB limit is common for multi-page uploads: a full application set, a rental agreement, a property document, or several certificates combined into one file. It is also a comfortable size for email attachments that open quickly on phones.
What happens when you compress
The pages are rebuilt as compressed pictures, trying high quality first and stepping down only as needed to fit under 500 KB. Because 500 KB is a generous budget, most scanned documents look very close to the original. A PDF that is already under 500 KB is returned unchanged.
Planning a combined upload
If a portal wants several documents in one file, first put them together with Merge PDF, remove extra pages, and then compress once — this gives better quality than compressing each document separately and merging later.
Common problems and how to fix them
Links in the PDF stopped working: compressed pages are pictures, so links and selectable text are removed — keep the original if you need them. The result is still slightly too big: remove a page or tick Black & white. Page size changed: it does not — each page keeps its original size.
Good habits
Merge first, compress last, keep both the original and the compressed copy, and check the final size shown before uploading.