When using my MacBook or my iPad, how do I change the line width and color when using the underline tool or the pencil tool?
Are you trying to edit a PDF or add annotations (comments) to a PDF?
You can't use your iPad to do that kind of an edit. If it's an annotation on an iPad, click the Underline annotation, and drag across the word(s). After you apply it, click on the word again, and you'll see options to clear the underline, to change its color, or its opacity. There is no option for changing line width.
On your MacBook, you'd be using either Adobe Reader or Adobe Acrobat. Ask in one of these forums:
Thanks, Steve. I'll give it a try.
..using the underline tool or the pencil tool
I am fairly certain that you are asking about the Commenting tools.
For Underline tool, there is no option to change the line width (thickness). But you can change the color and opacity. Additionally you can change the style in the desktop app.
For Pencil or Freehand Drawing tool, you can change the line width (thickness) in addition to color and opacity.
The key here is to change the properties of an existing comment once it is added to a page.
Acrobat Reader DC (desktop app) on your MacBook
Acrobat Reader for iOS (mobile app) on your iPad
Once you change a property (e.g. Thickness, Color, Opacity), the mobile app will remember the new value of the particular comment type for the next time.
Please let us know if you have additional questions.
Thanks, MobilDevCK. Between you and Steve I should be in good shape.