Most portals ask for PDF files under a size limit, readable at 100% zoom, with all pages in order and correctly oriented. Meeting all of that takes less than a minute when you follow the steps below.
The checklist
Scan with the phone scanner - auto-crop keeps edges straight
Check each page in the review screen; retake anything blurry or cropped
Keep it in color unless the instructions say otherwise
Choose A4 paper size unless the recipient specifies Letter
Name the file clearly - e.g. Passport_JohnDoe.pdf
If it exceeds the size limit, run it through Compress PDF
If pages are in the wrong order, drag them into place before generating
Need a signature? Use Sign PDF instead of printing and re-scanning
Before you upload
Open the final PDF yourself once and scroll through every page at normal zoom. If you can read it comfortably, the recipient can too.