SDKs or Commandline Tools to Convert DOC and TIFF to PDF in VB.NET

I've been working on a project that converts several file formats to a PDF in VB.NET/C#. The specific files are DOC, TXT, JPG, TIFF, HTML.

Actually I already have a solution for DOC/TXT to PDF using Bullzip PDF Printer by sending the files to the PDF Printer using VB.NET. However, each time it converts a file, MS Word opens and then closes once the file is sent to the printer. It really slows down the process.

As for TIFF to PDF, I haven't found a solution for it at this time.

I require SDKs or Commandline tools and not PDF convertion applications, since I need to integrate this function in my program. I prefer free or open source SDKs but commercial ones are accepted as well.

If anyone could point me to the right direction regarding this matter that would be much appreciated. I would also like to point out that I have done some research on this matter but I haven't found the right 开发者_开发知识库one yet.

Thank you very much.

Have you seen either iTextSharp or PDFSharp?
Both are open-source libraries for working with PDF files that work very well with .NET applications.

Aspose.Pdf is another option, if you're open to commercial software.