pencil tool

hi

while reading a paragraph in a pdf, if i mark the beginning of that paragraph in the shape of a bracket with the pencil tool and at the ending of paragraph i mark another bracket, some how those two brackets are inter connected, means if i wanna move one of the brackets any further they both move together. Further, if i wanna highlight or underline any of the text within that paragraph, the pencil tool prevents that action. it doesn't allow selection of text within those brackets. how i can prevent that inter-connection?

thank you for the support!