Short question: in some cases, you cannot highlight some text in a PDF using Preview, because it seems some "structures" is overlapping the text, so if you highlight a line or a few words, all the adjacent structures are all highlighted (it can be some structures that contain normal text or headings).
How can this be solved? This may need some apps to make those bigger structures' boundary smaller probably. Can it be solved by using Preview alone, or by Adobe Acrobat Reader that is free, or by Acrobat Standard or Pro that costs any where from $130 to $299?
Details: I have been using ebooks in the form of PDF files for a while, and find the searching of them very useful, and that there is no need to buy to buy highlighter pens, and it can be taken with me when I have my Macbook or iPad with me any where in the world, and carry 80 ebooks with me all inside the iPad when I am drinking a coffee at a cafe. But the limitation of highlighting is one issue. I also cannot highlight items in a picture or graph, which I could do with a physical book. I solved the graph / picture highlighting problem by draw "arrows" that point to the important points in the graph or picture. It works... although I might have 4 or 5 arrows pointing and it can look messy.