Doesn't always work, but it appears to on this giveaway.
On weekends GAOTD has a free game too (see link in upper-right). Sometimes the tip works on the games as well.
RE this particular giveaway.... I'm not sure I'd call it an "editor." Many so called editors don't actually *change* the pdf in any way... They just add to it. Even the eraser function doesn't change the pdf--it just paints virtual whiteout over parts of the document.