Hey guys!

I was provided artwork by designer in .PDF format ready for print but I later desided to make slight position change with some elements.
My designer is not available for now and I need to send file to printer after I make changes.

What is the right way to import .PDF into InkScape, make changes and save in a format that printer can use for prepress from get go?
There is 1-color printing process that will be done and I want to make sure saved file will be prepress ready. Must I convert colors for
offset printing or something and do something else I am unaware of?

Your guidance will be helpful to me.

Is the artwork in vector format? If not, Inkscape likely can't make any edits. (PDFs can contain both raster and vector images.)

You'll need to ask the printer what file format her or she wants, and what "prepress" means to him or her. There are so many tools for professional printers these days, and they usually use what they are familiar with. There's no "across the board" standard for these things.

If the 1-color printing process requires CYMK print model, Inkscape can't do that....at least not natively. Via extension a CYMK color PDF can be exported. Well, at least I know a previous version can export CMYK in a PDF. But that extension is under development, and I'm not sure if there's a workable version, at the moment. Hopefully they have one. Old version in this topic: viewtopic.php?f=11&t=5943 New version development: http://jonata.org/inkscape/outputpro/.

To me, it looks like that CMYK pdf extension has been abandoned.

Better to use Scribus altogether for this, instead of Inkscape (but check with Scribus' features first). Scribus can import pdf, and it can also do smaller vector edits (it's not very much fun to use its node tool..., but it works). Which kind of color properties it supports in detail is beyond my knowledge - it does support CMYK and color profiles, but as I never used spot colors, can't say how that would work.