On either 32 or 64 bit Windows, one must turn the LPR feature on, as it defaults to being not installed, by default. Startup your Control Panel and find the item Programs (called Programs and Features on Window 7). Click on Turn Windows features on or off. Wait for this menu to populate and scroll down until you see Print and Document Services. Click on the + on left side to expand it. Check the boxes to left of LPD Print Service
LPR Port Monitor. Close dialog by clicking on OK.
For 32 bit version of Windows, you can now use LPR from either a Command Prompt, or from within VisionDP or Proform Designer. If using a 64 bit version of Windows, one further step is required. After the above operation, you will now find a file lpr.exe in the folder C:\Windows\System32. This is sufficient if you are just going to use lpr from a Command Prompt, but to run it within another program, this file needs to be copied into the folder: C:\Windows\SysWOW64. You will probably need Administrator rights to do this copy.