When opening an exported PDF document from Adobe Illustrator or Indesign, make sure that your opening the PDF file in Adobe Acrobat and not Preview.
Issues can occur with text and images with PDFs being opened with preview due to the PDF version. When you export a PDF it lets you choose it's compatibility with previous versions of Adobe Reader and Adobe Acrobat. The older the version, the more compatibility but the larger the file.
If your still experiencing issues, try restarting the computer, restarting the program, and checking your links for the image and type. You can also consult these sections on Adobe's support page.