Hello all!
Thanks, Nita, for the ping
You are certainly on the right track. You are updating the correct language skin, and yes, language skins are honored in all outputs, including PDFs. So whoever told you that they aren't is clearly not terribly familiar with how they work. I have used the contextual cross-references from the Language Skins in many PDFs, and in many languages. Please note that not all languages work well with the contextual cross-references: Chinese, Japanese, and Hungarian in my experience so far.
But you are very right in that it is really hard to package up language skins for translation. The default English is nowhere to be found in any of the language skins, since it's pulled from some UI resource file. With regards to your screenshot about the French skin appearing in bold but with no location at first, that is normal. The bold indicates that Flare has default translations for the skin, but the location only appears if you create an editable version of that language skin. Essentially, the .fllng file you create contains overrides to the default translations, so it won't include all the French text (if you look at it in a text editor).
The real issue is making sure that all your ducks are in a row, so that the edited phrases are actually used in the outputs. The first thing to look at is, as Paul indicated, the language selected in your target or in your project. So if you open that Language tab in the target file you are generating, you either want it to have selected the proper language, or you want it to say "(default)" and then make sure that the Project Properties has the proper language selected. I prefer the latter approach, but either works.
The second thing is to make sure you know what the proper language should be. With regards to French, there are several options: French, French (France), and French (Canada). It looks like the language skin you edited is the French version. If you select French (France) in the Language tab, then your edits will not come through because the language selected did not match exactly. I suspect that this is the problem, since you are seeing French, but it's not the right version of the French.