That was Fast
The two PDF files shared as proof of the attack can be considered weapons:
[...] SHA-1 colliding files are currently breaking SVN repositories. Subversion servers use SHA-1 for deduplication and repositories become corrupted when two colliding files are committed to the repository. This has been discovered in WebKit's Subversion repository and independently confirmed by us. We noticed that in some cases, due to the corruption, further commits are blocked.