DOS cannot use any Windows drivers. All DOS programs have built-in drivers for all the printers they can support. As PDF was not developed until long after DOS had been replaced by Windows, there are no DOS applications that create PDFs.
About all I can think of is to use a PCL to PDF converter. Then get the DOS app to print to file (assuming it can even do that) and the converter can pick up up the file and create the PDF. There are many PCL converters available, for example:
http://www.verypdf.com/pcltools/index.htmlIf your DOS output consists of text only, without any printer codes, they also have a free converter:
http://www.verypdf.com/txt2pdf/index.htmBoth will run from a command line, so you could write a batch program that keeps looking for a PCL file. If it finds one, convert it and delete the original.
If your DOS app can only print to a physical port (e.g. LPT1) there are programs that can capture the output and redirect it to a file. Then you can use VeryPDF on that file. For example:
http://www.printfil.com/manualen/c7.htm