If you know the Mac platform well, then you know that PostScript is the preferred printing system for OSX and all its precedessors way back to the very early Macs. This comes about because Apple virtually invented PostScript printing and desktop publishing about thirty years ago partnering with Aldus, the inventors of PostScript (which later became Adobe). Whereas on Windows, PCL is the de facto print standard, although PostScript is also supported.
The problem is, there are cases where you will want to print to a printer that only supports PCL, and PCL drivers officially provided for the platform may be few and far between. Apple supplies a "Generic PCL" driver for OSX, but colour printing is not supported with this driver. We have a school customer with a pile of Ricoh photocopiers that don't have any PostScript capability and with which the Ricoh PostScript drivers wouldn't work. So, we needed a Ricoh PCL driver for the Mac, and officially, there are none.
But thanks to the Linux community there are good third-party drivers available, through Foomatic.
Go to this site (OpenPrinting) and there is information about OSX HP drivers. You could install these drivers if you have an HP printer. In this case we could have used these drivers for compatibility and they would probably be OK to a certain extent. However I did find another place where the Ricoh PXL drivers (PCL XL) can be downloaded.
The OpenPrinting page provides links to download the Foomatic RIP and GhostScript software, which you will need anyway, so go ahead and download those from the page.
Then go to OpenPrint's Ricoh downloads folder and find the driver for your Ricoh printer. In this case the MPC 4502 PXL.ppd file was the one needed.
Install Foomatic and GhostScript onto the Mac in that order, and then you need to make a small fix in the PPD file. Open it with a text editor, find the line that reads
*cupsFilter: "application/vnd.cups-pdf 0 foomatic-rip"
and change this to
*%cupsFilter: "application/vnd.cups-pdf 0 foomatic-rip"
then save the file.
You can then install a printer in the usual way, choosing the option to install a driver and opening the PPD file.
