How to Scan Documents to a Small, Readable PDF

For most documents, scan at 200 to 300 DPI in grayscale and save all the pages into a single PDF. That gives clear, printable text at a fraction of the size of a 600 DPI colour scan. If the result is still too big for an upload form, compress it afterwards.

Choose the Right Resolution

• 150 DPI: readable on screen and fine for most online forms. The smallest option that still looks clean.
• 200 to 300 DPI: the sweet spot for documents you may print, or that need to stay sharp when zoomed. 300 DPI is also what text recognition (OCR) works best with.
• 600 DPI and above: only for photos, artwork or tiny print you need to enlarge. The files are roughly four times larger than at 300 DPI.

The numbers add up quickly. An A4 page at 300 DPI is about 2,480 × 3,508 pixels. In colour, that's roughly 26 MB of raw image data before compression; at 600 DPI it's four times that.

Choose the Right Colour Mode

• Black and white: smallest files, perfect for plain printed text. Faint pencil, stamps and signatures can disappear, so check the result.
• Grayscale: the best all-round choice for documents. Keeps signatures, stamps and shading, and is noticeably smaller than colour.
• Colour: use it when colour matters, such as photos, highlighted passages, coloured stamps or ID cards that officials need to see in colour.

Scanning With Your Phone

You don't need a separate app. On iPhone, open Notes or Files and choose Scan Documents; on Android, open Google Drive and tap Scan. Both detect the edges of the page, straighten it and save a multi-page PDF.

• Put the page on a dark, flat surface so the edges stand out.
• Use even daylight or overhead light and avoid your own shadow; don't use the flash on glossy paper.
• Hold the phone parallel to the page, not at an angle.
• Check each page before saving, and rescan any that are blurred or cut off.

Scanning With a Flatbed or Office Copier

Look for the resolution and colour settings before you press scan, since many machines default to 300 or 600 DPI colour. Choose PDF as the file type and multi-page (sometimes called 'one file') so the whole stack becomes a single document. Scan-to-email often has a size cap, so lower settings avoid bounced emails.

Put Everything Into One Tidy PDF

1. If you scanned pages separately, merge them into one PDF and drag them into the right order.
2. Rotate any pages that came out sideways or upside down.
3. Remove blank backs of single-sided pages with the delete option in the Edit tool.
4. Check the file size. If it's over your limit, move on to compression.

Hitting an Upload Size Limit

Scans are exactly what compression is good at. In the Compress tool, switch on Target File Size and type the limit, such as 2 for 2 MB. The tool keeps the best-quality version that fits. Our guide on compressing to a specific size covers stubborn files.