How to Scan a Document for Upload — Small File, Still Legible
Application portals want scanned documents — degree certificates, ID cards, experience letters — as small files, often under 100–200KB, while still being clearly readable. The gap between a raw phone scan (frequently 3–8MB) and that limit trips up a lot of people. The good news is that most of the size is avoidable with the right settings, before you ever compress.
Grayscale beats colour, almost always
Unless a document's colour carries meaning (a colour photo ID, a stamped seal that must show colour), scan in grayscale. A grayscale scan is roughly a third the size of the same page in colour, with no loss of text legibility. This single setting often gets a document under the limit with no further compression needed.
Resolution: 150–200 DPI is the sweet spot
High-end scanners default to 300 or 600 DPI, which is overkill for screen-read documents and multiplies file size. For text documents destined for upload, 150–200 DPI keeps text crisp while cutting the data dramatically. Reserve 300 DPI for documents with fine print or small stamps that must stay sharp.
Use a document-scanner app, not a plain photo
Phone apps like the built-in scanners in iOS Notes and Google Drive, or Microsoft Lens, detect page edges, correct perspective, flatten lighting and output a clean, high-contrast page. A plain camera photo of a document is larger, skewed and harder for a portal to accept. The scanner apps also let you output directly as PDF or JPG.
Then compress to the exact limit
After scanning well, finish with the exact target: use the PDF compressor for multi-page documents or the image compressor for single-page scans, entering the portal's KB limit. Scanning smart first means the compression is light and the text stays sharp.
Frequently asked questions
PDF or image for a scanned document?
If the portal accepts either, a single-page document is simplest as a JPG image; multi-page documents should be a PDF. Match whatever format the form requires.
My scan is still too big after grayscale and 200 DPI — what now?
Compress it to the exact limit. A well-made grayscale scan compresses cleanly with legible text. Removing unneeded pages also helps for multi-page PDFs.
Why does the portal say my file is invalid, not just too large?
Usually format — it wants JPG or PDF and got something else, or a HEIC file from an iPhone. Convert to the required format first.