Why Is InDesign reading pdfs as missing fonts?

Because I often don't have a USB stick on me, I can't use my school scanner to scan PDF documents, so I have been using Adobe scan on my phone. However, when I put the PDF into my InDesign file, it resgesters as a missing font.

If I open the PDFs into Illustrator, and save them as a .ai file, I have no problems, but this is time consuming to do.

Please help :((