From Secure Soft:
XPS Signer main function is to sign XPS documents (see: XML Paper Specification) using X.509 certificates. Using this product you can quickly sign multiple XPS files (bulk sign) by selecting input and output directory. This is ideal for batch signing of large number of corporate documents rather than signing each one individually.
XPS Signer allows you to sign XPS documents without any need to purchase additional software. This dramatically reduces the Total Cost of Ownership (TCO).
Configurable Signature Behaviour - XPS Signer provides a fully configurable behaviour for its digital signatures.
Interoperability - Signatures produced with XPS Signer can be verified using standard XPS Viewer.
PKI Interoperability - XPS Signer is completely PKI neutral and will work with PKI components from any vendor (this includes CAs, certificates, CRLs, smartcards, etc.).