The 4 MB limit applies to the IRCC secure account, the PR Portal, online citizenship and the asylum portal.
Each field keeps only one file: join all pages of a document into one PDF first.
Check the limit shown in your own account: it is the one that applies to you.
How to do it with Requisito Listo
Open «IRCC secure account, PR Portal or citizenship».
Scan the pages with the camera or pick a PDF or photos you already have.
Put the pages in order.
The app builds the PDF under the size the portal asks for.
At the end you'll see a checklist: size, file weight, background and format. If something doesn't comply, it tells you what to fix before the portal rejects it.