It's relatively easy to see the fonts used when inside a PDF file. If you have Acrobat Pro, choose File > Properties > Fonts, and you'll see a list and also see how the font is stored. InDesign can also read this information. It would need to know it so it can print or export a placed PDF file.
If you have Acrobat Pro, you can also individually edit blocks of text and change the fonts. However, there is no way to search and replace fonts like InDesign can do with the Find Font dialog.