Aha! Well, I'm glad that we should be able to find a solution for you.
`lpr` is a command-line tool, which means that the easiest way to find it is to launch the Terminal.app (located in the /Applications/Utilities/ folder) and type `man lpr` (without the backticks).
Let's say that you had a file called "My Resume.pdf" on your Desktop and you wanted to print it.
You could go into Terminal.app and type:
lpr ~/Desktop/"My Resume.pdf"
and it would print it on the default printer.
If you have more than one printer, or if you want to specify different options than the default, that can be done, although it does get tricker.
Here is how you find the "Printer Name" that `lpr` needs. First go to System Preferences, then "Printers and Scanners" and select your printer.

Then click on the "Options & Supplies" button (shown above). That will open the window below:

The "Device Name" is what you are looking for. Note that lack of spaces (it uses '_' instead).
If I wanted to specify that printer, I would need to add `-P` (not `-p`) and then the "Device Name" so it would look like this:
lpr -P 'Kyocera_TASKalfa_2552ci' ~/Desktop/"My Resume.pdf"
I can see what other options I can use with `lpr` by using `lpoptions`.
This time I need to use a lowercase "L" and a lowercase "p" (unlike `lpr` which wanted an uppercase P) like this:
lpoptions -l -p 'Kyocera_TASKalfa_2552ci'
Those options tend to be different for different models of printers, so you'll have to figure out what the option is called if you want to specify things like black & white vs color or two-sided or not.
If you have questions, feel free to post a followup here. I'm tracking this thread so I should see it and will do my best to respond in a day or so (possibly sooner).