To debug a custom timer job in visual studio, I wasn't able to hit the debugger.
Is it necessary to add the .PDB file to GAC?
I tried doing the above, but it's not allowing to drag and drop this particular file.
Why do we need to add this file?
Drag and drop does not work in the assembly folder because of the shell windows explorer attaches to it. You can do 3 things to bypass this shell -
Copy the .pdb file via cmd in C:\windows\assemblyGAC_MSIL\yourassembly\yourassemblyversion\
Use gacutil.exe
Map the assembly folder as Network-Drive \server\c$\windows\assembly and then copy the .pdb just as you normally would
Here is a good article about debugging timer jobs. It's written for SP2007 but should apply to SP2010 aswell.