Gaaiho PDF Reader is a PDF reader by a company that has spent nearly 25 years making PDF-related editing, viewing, and several desktop publishing tools. Its PDF reader is loaded with features, which makes it ideal for expert users. The tool lets you open PDF files in multiple windows and panes, zoom the documents in different ways, add bookmarks, search for specific content, highlight text, add attachments and notes, fill in forms, annotate pages, etc. There is a PDF manager that helps find PDF documents on your computer. There are several other unique useful features too, such as integrated tools to share documents directly through Dropbox and Evernote.