The package used to provide macros that emulated the 'colour stack' functionality of dvips. The colour stack deals with colour manipulations when asynchronous events (like page-breaking) occur. At the time the package was written, pdfTeX did not (yet) have such a stack, though dvips had had one for a long time. This package was an experimental solution to the problem, and worked best with pdfeTeX. For current releases of pdfTeX (later than version 1.40.0, released in 2007), this package is not needed, since "real" colour stacks are available. The present pdfcolmk is therefore just an empty stub that does nothing at all, just in case there are still documents that reference it. The documented source of the original package is still available at the github repository.
Binary packages can be installed with the high-level tool pkgin (which can be installed with pkg_add) or pkg_add(1) (installed by default). The NetBSD packages collection is also designed to permit easy installation from source.
The pkg_admin audit command locates any installed package which has been mentioned in security advisories as having vulnerabilities.
Please note the vulnerabilities database might not be fully accurate, and not every bug is exploitable with every configuration.
Problem reports, updates or suggestions for this package should be reported with send-pr.