Was he so powerful with the dark side of the force that he could actually hide himself from the Jedi?

Actually, hiding one's signature in the Force doesn't really require that much power compared to some of the other abilities Sidious has displayed. And considering he is canonically stated as the most powerful Sith Lord of all time, I think the answer is yes.

In the EU, hiding your force presence was just a type of technique. Only a few characters seemed to know how, most notably being Jacen Solo. I imagine that sort of rarity continues.

I understood he was the most powerful but the reason I ask this is that I never truly followed the Star Wars universe. Yes I have seen all the movies and have watched the clone wars but never read the novels or anything like that.

Actually, I just read a DK Star Wars book to my son last night that said that's exactly what Palpatine did: hide his Force sensitivity from the Jedi. I had never read that explicitly stated in any of the novels, so it was nice to see it in writing.

I don't recall it being mentioned for Palpatine in a book, but it is in the Darth Bane trilogy. Bane's apprentice (I forget her name) was tasked with retrieving information from the Jedi Archives and had to disguise her dark side powers from the Jedi in the temple. She managed to pull it off for several days if I remember correctly.

I don't recall it being mentioned for Palpatine in a book, but it is in the Darth Bane trilogy.

From Labyrinth of Evil (Yoda's musing):

For that reason he understood just how dangerous this new Sith Lord was. He hadn't had a sense of that danger until he had fought Dooku on Geonosis. Then he understood. In self-exile for a thousand years, the Sith had not merely been waiting for an appropriate time to reemerge and exact revenge, but for the birth of one strong enough to embrace the dark side fully and become its dedicated instrument.

This was Sidious: powerful enough to hide in plain sight. Powerful enough to instruct his apprentice, Dooku, to expose him, and still remain hidden from the Jedi. And as arrogant as the Jedi. Convinced that his way was the one and only way.