When using the -P SPOOLER option, you can change fonts in the middle of a report when using the Windows spooler: simply select the new font via the W$FONT library routine while the print file is open. You can change fonts at any time, even mid-line, but make sure that WFDEVICE_WIN_PRINTER is set to TRUE before you call W$FONT. When advancing lines, the runtime uses the height of the selected font to determine the height of the line, and the font must be associated with the selected printer.
When using the -P PDF option, there are a number of runtime configuration variables (all prefixed PDF_) to enable you to change the characteristics of a PDF file without the need to modify your COBOL source. If you want more control over the PDF file output, you can modify your COBOL program and use the SET ENVIRONMENT statement to set any of these configuration variables.