Here is a short synopsis of my original problem:
When I installed Mint it automatically installed my HP970 Printer. The problem was that duplex - 2 sided printing - was disabled. I changed the printer driver using the utility in the Control Center to CUPS + Gutenprint and although duplex was now enabled it still refused to print on both sided of the paper. This is what I did to correct this issue:
Go to Synaptic and install the following packages:
hpijs
hplip
hplip-data
hpijs-ppds
hplip-gui - this isn't required but it does give you the HP Toolbox so you can check ink levels and such.
Open Terminal
Type sudo hp-check
This might output some dependency problems that you will have to resolve before you go to the next step. You may get an error about "sane" - ignore those for the time being.
Type sudo hp-setup
This brings up a small applet and will eventually ask what driver you want to install. I chose the one that starts with
dvr:///hpijs.dvr/hp-deskjet_970c-hpijs.ppd
If you go to Menu > Administration > Printing > Select the newly installed printer > Printer options > Double Sided Printing
it works. In fact I used the same method to install the same printer 4 times each with a different name and different default settings so I could just choose print quality by choosing the printer name:
HP970D - Print Mode: Draft
HP970N - Print Mode: Normal
HP970H - Print Mode: High Quality
HP970P - Print Mode: Photo
I've had issues with printing in other disros and have even resorted to going to the source by bringing up CUPS Server (localhost:631) but have always had problems installing and configuring HP printers. hp-setup works every time.











