Regarding Link Detox, links it diagnoses as Toxic are generally fine as they're either not indexed by Google or have malware/viruses/etc., but I recommend a manual review of any diagnosed as Suspicious. I used it recently to get started cleaning up our backlinks and some legit sites and blogs were under Suspicious simply because they didn't have many links pointing to them.
Let’s say you wish to block all URLs that have the PDF. extension. If you write in your robots.txt a line that looks like this: User-agent: Googlebot Disallow: /*.pdf$. The sign “$” from the end basically tells bots that only URLs ending in PDF shouldn’t be crawled while any other URL containing “PDF” should be. I know it might sound complicated, yet the moral of this story is that a simple misused symbol can break your marketing strategy along with your organic traffic. Below you can find a list with the correct robotx.txt wildcard matches and, as long as you keep count of it, you should be on the safe side of website’s traffic.

Beyond organic and direct traffic, you must understand the difference between all of your traffic sources and how traffic is classified. Most web analytics platforms, like Google Analytics, utilize an algorithm and flow chart based on the referring website or parameters set within the URL that determine the source of traffic. Here is a breakdown of all sources: