How to improve the quality of scanned documents
Note: This is general information, not a universal scanning specification. Follow the requirements of the organization that will receive your file.
A difficult-to-read scan can lead to OCR errors or a request to send the file again. Good focus, appropriate resolution, careful tonal settings and a final review can prevent many problems. Editing has limits: it cannot restore details that the capture never recorded.
Choose resolution for the task
There is no single resolution that suits every document. For ordinary text that may be processed with OCR, 300 dpi is a practical starting point. Small print, handwriting, stamps or enlargement can call for a higher setting; scan a representative page and compare both readability and file size. More pixels also increase storage and processing needs, and cannot recover details that were not captured.
The U.S. National Archives and Records Administration (NARA) recommends at least 300 dpi for office documents intended for possible OCR, and higher values for some detailed materials. Those are institutional recommendations for U.S. records, not a universal rule for personal scans or every submission.
Improve the capture before editing
Clean the scanner glass, align the page with the reference edge and check focus. A skewed page, dust or motion blur can be harder to fix after scanning.
Choose grayscale for faded or low-contrast text and annotations. Keep color when it carries meaning, such as colored stamps, marks or charts. Before using a black-and-white threshold, inspect signatures and faint notes: automatic conversion can remove them.
Make careful adjustments to an existing scan
If the paper original is available, scanning it again with better focus, alignment and lighting usually preserves more information than trying to repair a poor image.
A moderate contrast adjustment may make text stand out from a pale background. Crop excess margins while keeping the full page and any marks near its edges. Review the result at normal size and zoom in on small print; strong filters can erase faint writing or change the appearance of marks.
Review the file before sending it
Open the finished PDF and inspect every page for orientation, missing edges, readable dates and signatures, and the correct page order. If the recipient sets a file-size limit, compress a copy and compare its legibility before replacing the original.
For archival projects, use the specifications and quality-control process required by the institution. NARA’s scanned textual-record requirements vary by image mode and record condition; they do not automatically apply to consumer forms or other countries.
- Scan documents with a phone — Prepare and review page photos before making a PDF.
Related guide
For phone photos of pages, see how to scan documents with a phone.
Frequently asked questions
Is 600 dpi always better than 300 dpi?
No. A higher setting can help capture small details or support enlargement, but it also creates larger files. Test a representative page and follow the recipient’s or project’s specification.
Should I scan in color or grayscale?
Use color when color carries information. Grayscale can suit faded, low-contrast text or handwritten notes. Review stamps, signatures and pale marks before choosing a black-and-white mode.
Can editing make an unreadable scan clear?
Sometimes a careful contrast adjustment improves readability, but software cannot restore information missing from the image. If possible, rescan the original and compare the results.