Document guide
Black and white PDF: clean yellow paper and reduce scan size
For yellowed paper, compare paper cleanup with Grayscale and Black & white. The Black & white effect increases grayscale contrast; it can still contain gray pixels and does not guarantee a two-color bitmap. Check faint writing before applying an effect to every page, then adjust PDF size only if needed.
Steps
- Keep a copy and inspect the source
Keep the original PDF. If you need searchable text, working links, accessible tags, forms or signature validation, keep that version separately: these scanner workflows produce image pages.
- Compare paper cleanup with black and white
Open the document scanner and import the PDF or a document photo. On yellowed pages, start with White document, which aims to clean the paper background, then compare it with Black & white. Compare White document, Grayscale and Black & white on a page with faint text. Black & white is a higher-contrast grayscale effect. Strong contrast can lose pale writing or merge nearby strokes; judge the actual preview rather than expecting only pure black and pure white pixels.
- Review every page before export
Check decimal points, thin table lines, stamps, pencil notes and light-colored text. If the original paper is still available, better lighting and a new capture may help more than stronger processing. Export and reopen the PDF.
- Reduce size only if needed
For a large result, use the PDF size tool and select a sensible target. This is another image-based export. Inspect its result again; a smaller number of bytes is not a good trade if characters become unreadable. To compress a PDF and make it black and white, keep this order: apply Black & white, export, then run the PDF size tool on that export.
Paper cleanup and grayscale are different choices
White document aims to clean paper backgrounds. Grayscale removes color while retaining tonal differences. Black & white increases grayscale contrast and may still include intermediate gray values. Compare small characters, pencil marks and shaded diagrams instead of judging only the background.
Compression and document structure
Adobe documents scan enhancement and recognition as separate tasks. These LensUp tools reuse the scanner renderer and do not add a searchable OCR layer. A scanner-based PDF converter does not necessarily make a text-heavy file smaller: rebuilding text as page images can increase its size. Fewer colors alone do not guarantee fewer bytes.