Here is an example of how you can open Adobe PDF Reader (or another PDF reader) with a particular PDF document, and close the reader again.
static void pager_FindWindow(Args _args)
{
Filename pdfFileName = 'MyDocumentFile.pdf';
FilePath pdfFilePath = @'C:\XYZ\';
str adobeExe;
System.Diagnostics.Process process;
System.Diagnostics.ProcessStartInfo processStartInfo;
// Let Windows figure out the standard program and location for the PDF reader
adobeExe = WinAPI::findExecutable(pdfFilePath + pdfFileName);
// Start the reader process
new InteropPermission(InteropKind::ClrInterop).assert();
process = new System.Diagnostics.Process();
processStartInfo = new System.Diagnostics.ProcessStartInfo();
processStartInfo.set_FileName(adobeExe);
processStartInfo.set_Arguments(pdfFilePath + pdfFileName);
process.set_StartInfo(processStartInfo);
process.Start();
// Wait 5 secs. before closing the window
sleep (5000);
// Close the window
process.Kill();
}