I have recorded a short video explaining the required steps to embed a pdf (and other types) file into Blackboard Learn course, please review it and let me know if you have further questions.
https://eu.bbcollab.com/recording/d5c4bfb7b5104f988246f79fb0ad6d76
Remember the three steps
Share file.
Generate Embed code
Add Embed code to you Blackboard Learn course Item