Articles
Straight answers about PDFs.
Each guide solves the problem with tools you may already have, explains why it happens, and then shows how Keepsign does it. Sources at the end of every article.
NumbersThe cost of print, sign, scanDays lost a year, pages printed a week, and how many people still print just to sign.NumbersFake documents, by the numbersAI-made fakes grew nearly fivefold in 2025; 1 in 16 documents flagged. What to check yourself.NumbersPDF subscriptions, added upWeekly, monthly and yearly PDF plans added up over 3 years, priced Nov 4, 2026.PrivacyFree online PDF tools and privacyWhere your file goes, what policies promise, the FBI’s warning, and a 10-second offline test.SignaturesSign without printingThe steps on iPhone, Mac, Windows and Android, whether it counts, and when a drawn signature isn’t enough.SignaturesSign without invalidatingWhich changes a signed PDF allows, why most apps break it anyway, and how to add yours safely.SignaturesVerify a PDF signatureSigned or just signed-looking, how to verify it for free, and what to look at besides “valid”.SignaturesWhy a signature shows invalidThe real meaning of valid, invalid and unknown, and the fix for each cause.ReviewCheck if a PDF was editedSaved versions, signatures, fonts, covered text and metadata, and what each one proves.FormsFill PDF forms on iPhoneFree iOS tools, flat forms, the “Please wait” problem, and sending it without losing answers.SignaturesCertificate signatures on iPhoneWhat you need, why a profile in Settings isn’t enough, and three ways that work.ConvertPDF to Word on Mac, offlineThe methods that keep the file on your Mac, the ones that upload it, and a 10-second test.ScanRemove pen marks from scansColour dropout, the channel trick, healing tools and brush-and-fill, with their limits.ArchivePDF/A explainedPDF/A-1 to 4, the a/b/u levels, which to choose and how to validate for free.PrivacyRedact a PDF properlyWhy black boxes fail, where hidden text survives, and a checklist that proves it’s gone.SendCompress a PDF for emailThe real limits of Gmail and Outlook, why PDFs get big, and how to shrink one safely.
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