PaperCat is a document management application for home users that digitizes and organizes paper mail on a personal computer. The software reads scanned letters, identifies the sender and subject matter, and detects relevant data such as amounts, due dates, and open tasks. Each document is saved as a searchable PDF in a folder organized by year, with automatically generated file names, and can be retrieved through full-text search. Typical use cases include utility bills, meter reading requests, and other everyday correspondence. The workflow begins when the user places a letter in a scanner. PaperCat automatically detects new PDFs and images, makes the scanned pages searchable, and extracts key information from the content. The application displays amounts, deadlines, and pending actions so the user can determine whether a response is needed. If a reply is required, PaperCat can draft one using details from the letter, with placeholders for email or printable DIN 5008 letters. The application includes automatic AI analysis, a document assistant, task tracking, statistics, duplicate detection, and an archive question feature that answers queries by citing specific documents. The free version supports up to 1,000 documents for personal use. Paid tiers provide unlimited documents, commercial use, priority email support, and twelve months of updates. PaperCat uses a combination of local and cloud AI, with a local model keeping processing on the user's computer while only matching excerpts are sent to cloud services for calculations.