AskYourPDF is a top contender, letting you ask questions about your documents using ChatGPT. It comes with a Chrome extension, research assistant and other tools to help you get more out of documents and be more productive. It offers several pricing tiers for individuals and businesses, so it should be adaptable to your needs.
If you want to be able to analyze a wider range of documents, ChatDOC lets you ask questions of all kinds of documents, including PDFs. It offers more in-depth AI analysis, image analysis and even explanations of math formulas. A browser extension lets you upload documents easily, and a paid Pro plan offers more features if you're a power user.