There has been a lot of confusion on this topic, so let's clear it up!
If you intend on sharing your printer from a 32-bit server to 64-bit clients, you will need to ensure both 32 and 64-bit drivers are installed at the server. The issue however is that the server will not allow you to install 64-bit drivers. There is a really quick and simple solution.
1) Download the 32 and 64-bit Universal Printer Drivers from the manufacturer's site. DO NOT try and fiddle around with anything else.
2) Log into an as a domain administrator on a 64-bit PC or Server located in the same domain
3) From the command prompt run "printmanagement.msc"
---- Right Click "Print Servers" -> "Add/Remove Servers"
---- Enter the hostname of your server and click "Add to List"
---- Click "Apply" and "OK"
---- Expand the server you entered and load the "Drivers" child object
---- Right click the centre pane and choose "Add Driver"
---- Choose "x64" and "x86"
---- Complete the driver installation by assisting the installer to the INF files located in your 32 and 64-bit driver downloads you already completed
---- If you successfully installed the drivers, you should see both 32 and 64-bit listed under the drivers pane
4) It's now time to install and share the printer!
Browse to "Printer Management Console" -> "Printer Servers" -> "Server Name" -> "Printers" -> right click "Add Printer"
Complete the printer installation and select the drivers you installed when it asks.
5) Check the driver options
Select the printer you installed -> right click "properties" -> "Sharing" -> "Additional Drivers"
You should see both x64 and x86 drivers checked off; you're ready to roll!
If you do not see both checked off:
Select the printer you installed -> right click "properties" -> "advanced tab"
Choose the correct driver from the drop down list under "Driver: " and recheck the additional drivers options to verify.