Does Adobe Acrobat Reader DC allow to save the comment and markup toolbar on the default screen at startup and are there limits to markups with Adobe Acrobat Reader DC on PDF CAD drawings VS Adobe Standard?
Yes. Comment and markup refer annotations/markups tool in Adobe Acrobat Reader DC. But the Comment tools on the toolbar at startup or so call Quick Tools in Adobe are limited in Adobe Reader DC as shown below:
The first two icons (Add sticky note and Highlight text) which are the only markups on the Quick Tools toolbar and it can’t be customized in Adobe Reader DC. However, with one mouse click, you can get the full Comments toolbar with all the related tools:
Adobe Acrobat Standard DC and Adobe Acrobat Pro DC allow you to customize the Quick Tools toolbar.
However, Adobe Acrobat Standard DC and Adobe Acrobat Pro DC are fairly expensive if the only feature you’re using from them is to customized Quick Tools toolbar, I’d go with the one extra mouse click in the freebie Acrobat Reader DC.
Adobe Help > Use annotation and drawing markup tools to add comments in PDFs >
Add comments while viewing a PDF document