A red box around a document element means it is an image.
When a red box surrounds the entire page of a document it usually indicates the document has been scanned. A scanner creates a document where each page becomes an image with uneditable text.
Using the OCR (Optical Character Recognition) functionality you will be able to make the text in your scanned document editable.
If the OCR module is not available for you, you can purchase it here.
Click here to learn more about how to use the OCR feature.