Add annotations

If a paper document, but you can add annotations and sticky paste rubric, or press the confirmation seal viewing, the same thing as this is possible in the PDF file.
If the Adobe Acrobat Standard, (instructions add / remove / modify text), text annotation, stamps, such as drawing lines, various kinds (with marker color the background of the text) Highlights text annotation tools notes (icon balloon), for example you can add annotations.
In addition, some useful annotation can annotate pop-up, to convey properly the intent of the annotation.
In addition, if you use the Adobe Acrobat Professional, you can create PDF files that can be annotated even Adobe Reader.