@mrkrndvs Ultimately you could have more text than the original, so there's really no limit to the text beyond what your system will allow. I've not tried annotating .pdfs, but I suspect you could do it similarly to how I've done books via Kindle which let's me export/import data (example: http:/
For more substantive annotations I try to add them slightly off to the side in a different font/size, but you'll also notice that some of the blue highlights also have "hidden" annotations if you hover over them with your mouse. Things can be a bit crowded with the additional highlights added by Hypothesis (and other people), though I can choose to disable them if I want for my personal work. Hopefully it's relatively obvious based on what's on the page which parts are the original text and which are my additions. When excerpting articles like Watters', the canonical URL on the page points to the original, so all the SEO and links ultimately redound to the original.