Hi, I'm a software and database designer/developer with more than 30 years of experience. The past 20 years I was full time employed (in-situ) by two international organizations; the Inter-American Tropical Tuna Commission (San Diego, CA, USA), and the Food and Agriculture Organization (FAO) of the United Nations (Victoria, Seychelles).
I can develop your application using either the .NET framework or Delphi, whichever you prefer. For the datamatrix decoding, there are a few free libraries that can be used, including zxing (my favorite), libdmtx, etc. We would need to test them to see which perform best in your case. zxing can also decode PDF 417 relatively well. For the OCR I suggest we could use Microsoft's library for .net (if you prefer I work with this framework). There are several free OCR recognition libraries for Delphi.
Based on your description, I assume it would take about 10 days of my time to do this project, and I'm bidding accordingly.
If you think you may be interested in my services, please send me a PM. This way, we can further discuss your requirements and I can send you a copy of my CV for you to check references/experience.
Best regards.
Marco García