ChatPDF

ChatPDF is one of the simplest document-chat tools: drag and drop a PDF and start asking questions within seconds, no signup needed for light use. It returns answers grounded in the document with page references, plus an automatic summary and suggested questions. Students and academic researchers made it popular for quickly extracting answers from papers, contracts, and reports without reading the whole file.

The free plan allows two PDFs per day with limited questions; ChatPDF Plus (around $14.99/month) unlocks unlimited uploads and questions, larger files, and longer documents. A developer API lets apps add PDF sources, send chat messages, stream answers, and request page references programmatically.

Limitations: it performs well on direct lookup questions but struggles with synthesis questions that require connecting information across long documents. It handles PDFs only — Word, Excel, and PowerPoint files must be converted first. Uploaded documents go to ChatPDF's servers, so confidential material needs care, and answers should be cross-checked for important claims.

Go to chatpdf.com and drop a PDF — no signup for basic use. Create an account for history; upgrade to Plus for unlimited use.