PdfDing turns a scattered folder of PDFs into a proper library you can read, annotate, sign, and share from any browser. The viewer remembers exactly where you stopped in every document, so a manual opened on your desktop resumes mid-page on your phone, and progress bars in the library show how far you have read at a glance. Workspaces and collections group related documents, multi-level tags classify them, and starring, archiving, and bulk actions keep even a large archive tidy. Inside the viewer you can add text, highlights, and freehand drawings, then review and export your highlights and comments from dedicated sections and attach Markdown notes to a document. A signature you create once is stored on your server and waits for you on every device, ready to drop onto contracts and forms. Sharing a collection or a single PDF takes a link or a QR code, with optional access control over who can open it and for how long. Accounts are protected by OIDC single sign-on and two-factor authentication with TOTP or WebAuthn, and dark mode, an inverted color mode, and multiple layouts keep long reading sessions comfortable. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.