I am looking for a .NET library that is able to decode data from a PDF-417 barcode that is embedded either in an image file or PDF. At this point, I have only been able to
I've just successfully integrated the ZXing .Net port from java. It's not as powerful as other paid SDK's - for instance it couldn't detect barcodes in a rotated image. However, it's free and might work for you if you're on a budget. Generally you'll find the paid SDKs cost $400 and up. It has over a million downloads on Nuget, if that means anything.
https://github.com/micjahn/ZXing.Net