Read text from file works with text files only. In order to extract the data from a PDF document, you need to use Extract text from PDF. This is assuming your PDF documents are electronically generated and not scanned. If they're scanned, you will need to use OCR instead.
So, the correct approach is to use Get files in folder to retrieve the files, then use a loop, such as a For each loop on the outputs of the Get files in folder. When you do that, you get a %CurrentItem% which will store the one file for the current iteration. And you can use that in Extract text from PDF.
