Underline PDF

Underline text regions in PDF — line overlay per page.

Use Cases

Typical scenarios for Underline PDF — see if it fits before you start

For everyday edit tasks, Underline PDF is tuned for speed and fidelity to meet submission and printing needs.

Students and researchers edit lecture scans and papers in batches with Underline PDF, saving manual work.

For sensitive resumes and contracts, Underline PDF runs 100% locally — no upload, data cleared when you close the tab.

Upload — Click or drag PDF/images to the dashed zone. Multi-file and large files (<100MB per batch recommended) are read locally only.
Configure & process — Set pages, angle, password or quality, then hit “Calculate / Process”. Underline PDF runs via WebAssembly and pdf-lib in your browser — no server queue.
Preview & download — Check pages, size and thumbnails on the right, then download. Batch jobs download one by one; tweak and re-run if needed.

Page syntax: Use 1,3,5-7 or 1-10,15; empty means all. Out-of-range pages are ignored.
Privacy & size: Everything runs locally — no server upload. For large files, process in batches of 50–100 pages.
Fidelity: Fonts and vectors are preserved where possible. For scanned PDFs, run OCR/searchable PDF first, then convert.

Will files be uploaded? Is Underline PDF safe?

No. Underline PDF runs 100% in your browser via File API; no network upload, memory cleared when you close the tab.

Processing failed or download blocked?

Check page ranges, passwords and file integrity. If the browser blocks multiple downloads, allow “automatic downloads” or click links one by one.

How to chain with other edit tools?

Combine workflows: organize pages first, then compress/convert for submission, then protect/sign for delivery.

Upload file, process, download.

Alle Berechnungen laufen lokal in Ihrem Browser; es werden keine Daten hochgeladen.