I know this question is old and I hope you got your answer already but for the record:
Everything ignored by the default .gitignore can be rebuilt one way or another, I’ve also already done some playing with source control myself and it usually is fine as long as you recompile but if something breaks for someone (i.e. launcher not opening at all as you said) they usually have to:
1 - Right click in the .uproject file and select “Generate Visual Studio project files”
2 - Open the visual studio .sln file and open it
3 - In Visual Studio: press Build → Build Solution or Ctrl + F9
4 - Double click the .uproject file in order to open it.
I hope this helps someone in the future as this is the first result in Google when searching “binaries win64 pdb file ue4”
I was hoping I’d find an answer about whether it’s safe to delete them or not, I am almost sure it is safe to delete them but I don’t want to rebuild everything, here’s a screenshot of my Binaries/Win64 folder:
Note that every UE4Editor-ProjectName-0000.pdb has a size between 27 and 28MB and that the main ProjectName.pdb file has a size of 116MB, the whole folder takes 3.45GB and I’m fairly sure (at 99.99%) that sharing this with your artist would be completely pointless (unless you want to share the debug info, but even then you should probably only send the most recent one or something)