Adobe DC Pro - Can't draw multiple connected lines close to each other on same pdf page

I am trying to draw multiple connectedt lines on the same building floor plan. When i try to draw a new connected line close to a previosu line or within a previously drawn line the mouse pointere will select one i previously drew or move the pdf page itself rather than start a new line. 

At the moment I have to drawa the approximate shape outside or on the edge of the page and then drag it ver one point at a time.

Apologies if i am missing something obvious but any help would really be appreciated.

Thank You