As you have Acrobat installed, and the plufgin installed, you must configurate K-Meleon.
1) Look at Edit > Advanced Preferences (F2) > File Types, and change the action if .pdf is in the list. Take Default if you have already set Foxit Reader as default pdf reader (When launching it, it's set automatically), if not, you can 'Open with this application', and browse to set Foxit Reader.
2) If not in the list, Edit > Edit Mimetypes > New Type
Mime Type = application/pdf
Description = Portable Document Format
Extension = pdf
After validating, verify if 1) is set
Remark:
I have had some problems, under w98se and with the previous K-Meleon version (there were no Advanced preference and it was 1.7.x Mozilla version) even the settings were correct. The problem was due to the adobe plugin, and I have deleted the adobe plugin dll to make it work.
Now I haven't Adobe installed,n and it's ok. Under xp, I have the two installed and it seems there is no more problems.
A+
Mozilla/5.0 (x11; U; Linux x86_64; fr-FR; rv:38.0) Gecko/20100101 Ubuntu/12.04 K-Meleon/76.0
Web:
http://jujuland.pagesperso-orange.fr/
Mail : alain [dot] aupeix [at] wanadoo [dot] fr
Ubuntu 12.04 - Gramps 3.4.9 - Harbour 3.2.0 - Hwgui 2.20-3 - K-Meleon 76.0 rc