You can review PDF-documents in Adobe Acrobat or in Adobe Reader, provided your documents are review-enabled.

For Adobe Reader 8 or Adobe Acrobat 8:

1. Open your PDF document.
2. Choose View > Toolbars > Comments & Markup.
   You can see the Comment & Markup toolbar:
   
3. Use the new toolbar to mark the text or the images you want to comment on. You can highlight the text or draw a box around it.
4. Right-click the markings in the document and choose Open pop-up note.
5. Type your comments in the pop-up note.
6. Save and close your PDF.

You can now send your reviewed PDF back to the technical writer.

For Adobe Reader DC or Adobe Acrobat DC:

1. Open your PDF document.
2. To the right, you see the tools pane. If it is not visible, press Shift+F4 to make it visible.
3. Press the Comment button in the tools pane.
   The Comment toolbar now opens:
   
4. Use the toolbar to mark the text or the images you want to comment on.
5. Right-click the marking in the document and choose Open pop-up note.
6. Type your comments in the pop-up note.
7. Save and close your PDF.

You can now send the reviewed PDF back to the technical writer.