Preview has strange behaviour when adding and editing annotations, even in Catalina. It quickly gets upsetting and unreliable.
annotation
One of the more confusing features of PDF apps, as none seems to work quite the same, and removing them isn’t quick or simple.
For less than the cost of a year of Adobe Acrobat Pro DC, this is the first choice for anyone who needs more powerful editing tools.
For around half the cost of a year of Adobe Acrobat Pro DC, you can have a superb PDF reader with good general annotation and editing tools.
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The Eclectic Light Company 