Lumen – Offline PDF Search

Find any word inside any PDF on your phone — instantly, and completely offline. Lumen is a privacy-first PDF search app. Point it at a folder of PDFs and it builds a full-text search index right on your device. Search for a word or phrase and Lumen shows you every match: the file name, the exact page number, and a highlighted snippet of the surrounding text. Tap a result to jump straight to that page. No internet. No accounts. No tracking. Lumen has NO internet permission at all — your documents and your searches never leave your phone. — WHY LUMEN — • Full-text PDF search — search the contents of your PDFs, not just file names • Find text in scanned PDFs — built-in offline OCR reads scanned and image-only documents so you can search them too • Jump to the exact page — every result links to the page and highlights the match inside the built-in PDF viewer • 100% offline — works on a plane, in a basement, anywhere, with zero signal • Truly private — no internet permission, no analytics, no ads, no data collection of any kind • Fast — results appear as you type, even across hundreds of documents • Lightweight on storage — Lumen never copies your PDFs; it reads them in place — HOW IT WORKS — 1. Pick a folder of PDFs (Storage Access Framework — your files stay where they are) 2. Lumen indexes the text on every page in the background 3. Search any word or phrase and get filename + page number + highlighted snippet results 4. Tap to open the PDF at the right page with the match highlighted — PERFECT FOR — • Students searching lecture notes, textbooks, and research papers • Lawyers and paralegals searching contracts and case files • Researchers and academics searching journal articles • Anyone with a phone full of receipts, manuals, statements, or scanned docs — PRIVACY YOU CAN VERIFY — Lumen ships with NO internet permission — you can confirm this in the app's built-in Privacy Audit screen and in the app's permissions on Google Play. No Firebase, no analytics SDKs, no crash reporting, no advertising. Your search index lives in a local database on your device and nowhere else. Delete it any time from Settings. Lumen is open source. Source code: github.com/royalgillz/Lumen Keywords: PDF search, search PDF, find text in PDF, offline PDF reader, full text search, document search, PDF finder, scanned PDF OCR, search inside PDF, private PDF viewer, PDF text search offline.