I\'m looking for a way to generate PDF files using the standard PrintDocument and Graphics (GDI) classes in .NET. As far as I know, the only way to do that is by printing to
Amyuni PDF Converter does what you need, it provides a Microsoft certified printer driver that you can fully manipulate using a COM interface or .net assembly, and you can use standard GDI (or Windows.Forms classes) to generate your PDF files (you probably checked on Amyuni PDF Creator, which is a custom API as you stated in your comments to this answer ).
There are several companies who create document format conversion tools. Several of them use printer drivers to "print" the document into the format desired. Look around for tools that can convert from Word documents to PDF. One of these should have the kind of driver you need, and some will offer an API that allows you to control filenames and such.
The C1Pdf component does this. It has methods that mimic GDI plus (DrawString, DrawImage, etc) and generates PDFs. It does not install or require any printer drivers. Here's a link to the documentation in case you want more detail:
http://www.componentone.com/newimages/Products/Documentation/WinForms.PDF.pdf