Task: Adobe PDF reading
Reading accessible PDFs should cause few problems with built in magnification and text reading in Adobe Reader. However, there are times when inaccessible PDFs developed in Adobe Acrobat need to be scanned and read with optical character recognition. This is especially true if the document appears as a picture. 
The results (as shown below) are not always totally successful for those who wish to read the content on a screen with text to speech or a screen reader. Advice about making these types of documents accessible can be found through the guides, TechDis Accessibility Essentials 4 , Adobe accessibility webpages and their quick reference card for making accessibe PDFs from Word.
Scanning documents (using a flat bed scanner or sheet feed scaner) so they can be read aloud is not as simple as it sounds. Not all parts of a page can be transcribed by optical character recognition software and not all books or journals etc have clear text. Images, diagrams, equations, tables and many other items remain unreadable sometimes with numbers and odd symbols appearing or just gaps in odd places. This impacts on ease of reading and often it would be much easier if the document was available in accessible electronic format.
Scanning takes up time and expertise if it is to be done well. Some PDFs are just an image and many technologies cannot decipher the content. TextHelp Read and Write uses Screenshot Reader for small bits of text within graphics but this has to be mouse controlled and is not designed for those who are blind.
One stop scanning with screen reading is available with Kurzweil Scan and Read or high end optical character recognition software may be preferred such as AbbyFine Reader or OmniPage Pro used alongside JAWS or other screen reader packages
Allgraphicdesign.com offer a good selection of general scanning hints and tips and Wayne Fulton offers some tips about the use of Optical Character Recognition (OCR). AbilityNet offer guidance about alternative formats as do JISC TechDis
