DigiSigner

DigiSigner is a free software application you can use to open and view PDF documents, as well as to apply and verify digital signatures using X.509 custom certificates. It can be used as a typical PDF reader too.

Setting it up is a fast and easy job, where the only notable aspects are that the utility offers to set itself as the default PDF viewer and that Java must be installed. It's wrapped in a well-structured interface that lets you open PDF documents from file or URL.

Digital signatures can be made visible or invisible. It's possible to add an existing key store from file, smartcard or USB stick key store, or to put together a new one on the spot by specifying personal information, certificate validity, key size, hash algorithm, and password.

The appearance of signatures can be customized by embedding graphic files, setting the signature text font, adding a frame, logo or distinguished name, and others. A batch mode is available for signing multiple PDF files at once.

Moreover, DigiSigner is capable of swiftly verifying digital signatures on its own, revealing any modifications, the user who signed it, and whether or not the date and time come from the signer's computer.

The program's functionality doesn't end here. It enables you to insert text and images, rotate pages, zoom in and out, use a basic search function, view document permissions and general properties, extract text and export it to TXT format, send the PDF file as an attachment in the default email client, as well as print data.

It worked smoothly in our tests, without hanging, crashing or prompting error messages. CPU and RAM consumption was minimal during its runtime. To wrap it up, DigiSigner provides users of any skill level with an approachable solution for digitally signing PDF documents to protect copyright.