This is qpdf version 9.1.rc1, a release candidate for 9.1.0. For a full list of changes, please see the release notes. One substantial change in 9.1 is the addition of build-time selectable crypto providers and, in particular, crypto provided by gnutls. While it is still possible to build qpdf without gnutls and use its native crypto implementation, using the gnutls implementation provides the advantage of relying on a more scrutinized and tested crypto implementation. This is described in detail in the manual and referenced in the release notes. In addition to this, there were some fixes to prevent qpdf from breaking digital sigantures, and several APIs were added to provide more detailed information about file offsets of source and generated files as well as object renumbering information, potentially useful for applications that need to operate on files lexically after they have been generated.
This release candidate is provided primarily for people who want to test their build or packaging of qpdf with the new crypto providers. A 9.1.0 release will follow in about a week if all goes well.