How to produce/generate a .pdb (debug symbols)?

Question

I'm using Unity. I've loaded an open source Node editor pluggin for it from here. My problem is - this pluggin folder does not contain any .pdb, so I cannot debug. What I've checked/tried:

• My solution configuration in Visual studio is set to "Debug".
• I've downloaded & tried to use "master" & "develop" branch of this plugin from git.

How can I get/produce a .pdb for this code to be able to debug it?

PS: (May be it's relevant to my issue) I've noticed, that only few of .cs files are shown in Solution explorer in Visual studio:

for example, none of framework files are present in Solution explorer:

Answer 1

I'll not accept this answer, 'cos it doesn't actually answer my initial question. But it solved my particular problem (actual only for Unity), so I post it:

My actual problem was an inability to debug code because of non-working breakpoints with message: "The breakpoint will not currently be hit. No symbols have been loaded for this document.":

And it was solved by simple using "Debug \ Attach Unity debugger" instead of familar to me "Debug \ Attach to Process" in Visual Studio =)