UnityPDF is a free toolkit for manipulating PDF files in various ways.
It's generally very easy to use. If you'd like to merge multiple PDFs, say, drag and drop them onto the program window, click Actions > Merge, enter a name for the combined file, and UnityPDF will create it for you.
There are other actions to extract all or selected pages, divide one file into several, rotate every page in a file, insert pages from one file into another, password-protect or set permissions for your PDFs (disallow printing/ editing/ copying/ annotations, and so on), display or clean metadata.
The UnityPDF interface is very basic. Once you've chosen your target files, there's no drag and drop support to rearrange them; you must select files individually and use Up/ Down buttons. There's no option to view a target PDF, or check its file properties. And once you've run an operation, the program won't open the output folder for you to view the results: you have to browse to it manually.
The "Display Metadata" option is especially poor. We thought that turning this on might display a pane in the program window, displaying the metadata of the currently selected file. But no...
Instead, a plain text box opens, displaying the metadata of the first file in your list, often in hard-to-read raw XMP format. Click OK, that box appears, and the same happens with the second file, then you repeat the process with the third, the fourth, the fifth...
You had 100 files in your list? Unlucky. There's no way to cancel the process, so you must either click OK 100 times, or close the process with Task Manager.
Despite that, the core functions to merge, split or divide PDFs work well and are easy-to-use, and UnityPDF's password-protection and cleaning features also delivered for us. If that's enough for you, then it's worth giving the program a try.
Versiom 126.96.36.199 "added the Russian translation".
UnityPDF's interface is poorly designed, but there are some worthwhile features here. The "Divide" function makes it simple to split large PDFs into smaller chunks, by page or file size, and it's equally easy to set document passwords and permissions or clean metadata. If that sounds appealing, go take a look.