That's quite tricky under Unix, at least I think it is.
Finding the files in a directory is fairly easy - OS-DIR gives you the list of files, you can import them into a Temp-Table and then process each one individually.
However, printing each file is the difficult part.
Under Windows you would have a procedure than checks the file extension and then launches a routine that prints files of that extension. However, even this is not easy as you will have multiple extension types that each require different methods of printing.
For example, printing a .PDF file under Windows is different than printing a .DOC file or a .TXT file.
Under Unix, you will probably have difficulties in being able to print off each file format. I have only had experience in printing flat files on Unix printers, but I am guessing that this is very tricky indeed. Simply catting the file and piping it through lp won't work here, which is how Unix files are generally printed.
You also have a problem in what to do with file extensions that your program does not recognise. You might need a list of valid extensions with print routines and anything else might be treated as an exception that cannot be printed.
Do you really want to be able to print all files in a single directory, no matter what the extension? Or do you have a list of file extensions that are likely to be in the directory and want to print those?
Have you searched Progress Talk or PEG to see if someone has already found a solution?