I don't remember how I did it, but it wasn't difficult at all.
I was as pissed as any of you, and my first reaction was to send them to the hell. At this point I downloaded all my content and didn't do anything else. Then I cooled down and started thinking about it, reading feedbacks on the other free services, etc. And I noticed that people who were very inspired by them in the beginning gradually came to realization that it wasn't a free lunch, and the services were not as rosy as they appeared in the beginning. And it happened way more quickly than in the case of PB: months vs. decades.
Then I thought that if I stop using PB, all the links I posted everywhere over the years will be broken, and this would be a great disservice to those I posted them for.
So, considering all of the above, I decided to subscribe to their basic paid service. It's about $60 per year, IIRC. Not a big deal even with my VERY modest use of it. Frankly, this decision of mine was a great surprise to myself. I absolutely hate being pressed, blackmailed or extorted, and tend to have quite a violent reaction to it. But in this situation I just tried to be rational.
Frankly, I suspect PB will go under in the near future. Not because they decided to switch to paid services, but because of the way they did it in the beginning, before the old management was fired. Their decision makers didn't have any common sense, diplomacy or customer skills. The new policies are much more reasonable, but the majority of the customers were so pissed off that they don't even want to think about it now.
So while PB works, I'll use them. No, I'm not going to be loyal to them. Just business, nothing personal.