PortableNotary

PortableNotary is a Java-based application that enables you to check PDF signatures and secure important documents with a password, in order to protect them from other users you share the computer with, as well as to safely transfer files to other people over removable storage devices or the Internet. It can be used from a command-line interface.

No setup required, besides Java

Provided that you have Java installed on your computer, you don't need to set up anything else. This means that you can save the downloaded executable file anywhere on the hard drive or keep it stored on a USB flash disk, in order to directly run it on any PC with Java.
It doesn't add new entries to the system registry or create files on the disk without asking for permission. In order to uninstall it, you just have to delete the .exe file.

Add keystore passwords and verify signatures

As far as the interface is concerned, PortableNotary opts for a standard window with a simple design and layout, where you can resort to the built-in file browser to locate and open PDF documents. Their content can be examined in a built-in viewer.
Once a PDF file is opened, you are prompted by a dialog box to insert the keystore password you wish to apply for document protection. Afterward, you can inspect the file signature as well as modify the keystore password if necessary, in addition to the keystore path on the hard disk.

Evaluation and conclusion

Unfortunately, PortableNotary hasn't received updates for a long time and didn't work with the most recent edition of Java Runtime Environment in our tests. It worked with an older version, however, without triggering the operating system to hang, crash or prompt errors. It needed a minimal amount of CPU and RAM to work properly, so it didn't hog system resources.
To conclude, PortableNotary doesn't have a particularly rich set of features and doesn't work with the latest Java release. Otherwise, it offers a straightforward solution for password-protecting PDF files and verifying their signatures.