I don't currently have any sort of notebook. Instead, for general notes, I prefer A3-sized loose sheets of paper, since I don't really want to use double the table surface to have both verso and recto in front of me, I don't like writing on spiral or perfect bound notebooks, and I already catalog my papers into 3-ring binders.

if I'm debugging something, and I'm putting silly print statements to quickly troubleshoot, should I document that?

My read of the linked post is that each discrete action need not be recorded, but rather the thought process that leads to a series of action. Rather than "added a printf() in constructor", the overall thrust of that line of investigation might be "checking the constructor for signs of malformed input parameters".

I don't disagree with the practice of "printf debugging", but unless you're adding a printf between every single operative line in a library, there's always going to be some internal thought that goes into where a print statement is placed, based on certain assumptions and along a specific line of inquiry. Having a record of your thoughts is, I think, the point that the author is making.

That said, in lieu of a formal notebook, I do make frequent Git commits and fill in the commit message with my thoughts, at every important juncture (eg before compiling, right before logging off or going to lunch).