PDF Combine software (version 6.1.0.135) allows users to combine multiple PDF files into one document quickly and easily. The software supports a wide range of input formats, including PDF, DOC, TXT, RTF, XLS, and more. The software also offers advanced options, such as the ability to add bookmarks, set page ranges, and define output settings. Additionally, PDF Combine supports batch processing, allowing users to combine multiple files at once.