I letter comics for digital publication. My typical workflow looks something like:

TIFF source file (color art)

to

SVG file with the source file embedded (this is the file I actually do the work on)

to

Exported PNG

to

Final, lettered TIFF

Since I can't export directly to TIFF, I use PNG so that every step of the process is lossless, then convert to TIFF with another program.

My major issue, though, is that I'll soon be doing this sort of thing for print work, and for that I'll need to provide CMYK TIFF files. There's nothing stopping me from buying Illustrator and using it, but I learned to letter in Inkscape, and I'd rather not have to relearn everything I know if I can help it.

So, the question: How do I get a TIFF with CMYK colorimetrics somewhere out of this workflow? The TIFFs I work from are CMYK, but I don't actually have any means of saving a CMYK TIFF, as far as I can tell. I have tried to convert the final, RGB file to CMYK using GIMP with the installed Separate+ plugin, but I seem to have run into some compatbility issues there, as the only Separate+ compilation I can find only works with 32-bit Windows, and I'm running a 64-bit system.

Um... help?

Perhaps Scribus could help? It`s another OpenSource program but with better cmyk support.

Still, isn`t there a way to add subfiles to tiff`s? Lost track of that format but I think it`s (was) possible to add "annotation" to the original file - which, if possible, could spare you from all of this colour voyage / due to my presumption that lettering means adding (usually black) text in dialog balloons and similar.
Also, If needed, you may search for Lazur RH topic about custom palettes, where you could learn how to add Pantone colors i.e. which should be pretty much close to the printer`s demands. This is in case you`re using colors for text, since this way you`ll stay close to the cmyk colors and later conversions would not bring much difference.

try this

install image magick
and run this batch

convert thefileasexportedfrominkscape.png -colorspace cmyk newname.tiff

I belive it was Ragnar.
pantone palette
how to create a custom palette by hand 1.
how to create a custom palette by hand 2.
more explanation on creating a custom palette by hand
swap colour extension

I personally don't use custom palettes, all my finetuning that I add to my objects are through the stroke and fill panel.

On the original topic: cmyk and pms are two different things.
Cmyk stands for cyan magenta yellow and black, which are the base inks of regular printers.
There are printers where you can use more kind of inks, which extend the colour range, thus needs a custom colour space.

Pantone, is a colour matching system -pms-, for spot colours.
All inks used in cmyk printers have a pantone code.
You can define colours by their pantone numbers, then request from the printer to use those exact colours as base inks.
(Which is good for cost-effective industrial use.
If you print gazillion copies of the same image on a regular cmyk priner, one ink would be used more.
Thus refilling the printer with ink should be done more often.
Also, there are colours out of the regular palettes you can't set apart from pantone, like metallic gold, 871C)
To do that, you have to use a custom colour mode.
I know it can be done through photoshop, not so sure if it could be done through illustrator -namely to produce pms pdf-s.
In photoshop it's something like turn the colour mode to pms, and define each colour for monotone/duotone... images.

I belive regular cmyk would be better for printing comics.
I don't have a good workaround for that, but there was an extension which could export images from inkscape with cmyk profile.

@ Lazur URH
Sorry mate, lapsus.

I`ve just crossed to that post...
viewtopic.php?f=11&t=5943&start=25#p57310

Another tool that can be used is tifficc (http://linux.die.net/man/1/tifficc). You can find a Windows binary for it and I'll assume that there is a Mac build somewhere. Once you export your png from Inkscape then you can use Gimp or something similar to convert the rgb png to an rgb tiff. Afterward, use tifficc to convert the rgb tiff to cmyk tiff.

Ex. tifficc
Linux terminal> tifficc -o USWebCoatedSWOP.icc input_rgb.tif output_cmyk.tif

Use imagemagick to verify the file (it should read cmyk for the colorspace).
Ex. imagemagick
Linux terminal> identify -verbose rgb_cmyk.tif