I have a Canon Pixma 4600 , which I'm trying to set up to as full funcionality as possible.

So far I have the following config working quite well.

I downloaded a Cups ppd from canon at http://software.canon-europe.com/software/0028476.asp there are two deb packages , downloaded them both and let the package manager install them.
ppd fil(s) now in /usr/share/cups/model .

I have tried editing the ppd to include the Advanced settings suggested here https://help.ubuntu.com/community/Ha...nonPixmaIP4200 , to get a higher dpi , but when I select the edited ppd in printer config , settings , make and model , change . the test page doesn't print? I only get a successful test page withe the original ppd , dpi 600.
Is editing the file corrupting something? How can I test the dpi against that specified in printer config? As the printout looks good , better than I expected for 600.