You can encrypt your pdf files by this application.

Encrypt: Enter your password and then click on the "encrypt" button.

Extract: Enter page numbers for extracting then from an existing pdf and save them like a inew pdf file.

Combine: Select first and second pdf then combine them easily.

Please note that maybe some difficult pdf files will not work by this application. But these problematic files are very little.

All new files will be located on ".../Download/pdftools" directory.

Have fun!