Applies to 

Readiris 25 Essential and Elite versions. 

• Digital PDFs contain actual text and image objects. You can search, select, copy, and edit the text (with appropriate software). These files are created directly from digital sources and are ideal for further editing or text extraction
  
  
• Analog (Image-only) PDFs are essentially photographs or scans of documents. The content is "locked" in an image layer, so you cannot search or select text unless you use Optical Character Recognition (OCR) to add a text layer. These are not editable as text and are not searchable by default.

1. Readiris PDF processes existing images or scans using OCR to convert the images of text to actual text. This text can then be manipulated or processed to an output file that contains that actual text.  
   
   
2. When opening an analog PDF the program will ask if you want to perform OCR. Generally the answer is yes.
   
   
3. When opening a digital PDF there is no need for OCR because the original document already contains "live" text that is opened as such in Readiris PDF.

In some cased a particular PDF may have an unusual layering of text and image and produce poor results. In that case export as an image (TIFF for multipage) and reopen that file in the software to perform OCR.