how to make a program that sends pcl to the printer from Mainframe

When I do it in COBOL, I put the PCL commands in the source code. I know very little able Easytrieve so cannot help you there.

Most PCL escape sequences use plain ASCII graphic (printable) characters (in the range 0x21 -> 0x7e), the obvious exception being the Escape character itself (0x1b).

I too have no knowledge of Easytrieve; provided that it has a means of writing a stream of ASCII characters (in this sense, I'm using ASCII to include the C0 control code characters in the range 0x00-> 0x1f, and 0x7f), you shouldn't have a problem.

Having said that, a few escape sequences have binary data associated with them; this binary data could include bytes of any value (i.e. in the range 0x00 -> 0xff).

If you need a decent looking form overlay with a logo, etc. Then, I recommend using PCLWorks's Img2PCL program to easily generate a form overlay macro or automatic overlay. Then, all you need to do is insert the appropriate PCL to invoke the macro and the absolute coordinates to position the variable data text.

It's always helpful to indicate what type of document(s) you are talking about. If they are highly structured (claim forms, invoices, etc.) or unstructured (reports, lists, ?).