Review comments on PDF4

"Assistive Technology" -> "assistive technology"

I suggest changing the text of the link  working example of marking a
background image as an artifact (Word
file)<http://www.w3.org/WAI/GL/2011/WD-WCAG20-TECHS-20110310/working-examples/PDF4/decorative-image.docx>"
to " working example of creating a decorative image  (Word
file<http://www.w3.org/WAI/GL/2011/WD-WCAG20-TECHS-20110310/working-examples/PDF4/decorative-image.docx>)",
since the current text makes me think that there is a way to mark the image
as an artifact from Word.

Change the test procedure: "For each image that is purely decorative" ->
"For an image that is purely decorative"

Change"Use a tool that exposes the document through the accessibility API
and verify that decorative images are marked as artifacts." to "Use a tool
that exposes the document through the accessibility API and verify that the
decorative image is not exposed through the API."

Remove the reference to tabbing to the image from this test procedure step:
"Read the PDF document with a screen reader, listening to hear that the
decorative image is not announced when tabbing to the image (if it is
tabbable) or when reading the content line-by-line."

(If the image is the only content of an interactive control, by definition
it is not decorative; if it is part of the content that also contains text,
it gets very complicated to explain what the requirement is.)