Is there a trial version?
Yes, you can download it here. The demo has the same features as the full version, but only extracts annotations from every other page of the PDF.
Can Highlights extract annotations made with other apps?
Yes, Highlights uses standard embedded annotations which are supported by most PDF readers on both OS X and iOS.
Some PDF apps (including Skim) and most reference managers use non-standard annotations which are not compatible with Highlights. However, most of these apps allow you to export the PDFs with embedded annotations which will work in Highlights.
How do I customize what is included in each annotation?
Under Customize in Preferences, you can set which information should be included in each annotation (including author, modification date and color category).
How do I use reference lookups?
Check out this tutorial.
How do I use color coding?
Color coding allows for categories of annotations sorted by color. By going to Preferences –> Colors you can see the current order in which the colors will be sorted. You can reorder the sorting and rename the each color to represent a category.