Google's Gary Illyes said in the comments section of this Google+ post that links within Adobe PDF documents do pass PageRank.
Gary wrote:
Dan, you asked me in Sydney and I told you they [PDFs] pass PageRank.
The question came up as it relates to a security company named Sophos uncovered link spammers cloaking PDF documents with links and keywords and then redirecting users to spam sites.
Dan Petrovic commented on Glenn's post on Google+ saying "last time I checked PDF files didn't pass PageRank."
Which Gary from Google came in and said "you asked me in Sydney and I told you they [PDFs] pass PageRank."
Also, Google said so in this blog post from 2011 "generally links in PDF files are treated similarly to links in HTML: they can pass PageRank and other indexing signals, and we may follow them after we have crawled the PDF file."
Forum discussion at Google+.
