Even with the best pasting, soaking and applying, wallpaper will stretch and distort then re-tighten as it dries out. This might be a lot or a little, depending on the weight and type of the wallpaper. Some go on like a charm - like the wallrock stuff - but recently I helped a friend with a fancy-pants designer paper and oh boy there were bubbles, all of which stretched out overnight.
The stores sell overlap adhesive in tubes, which is thick PVA glue, and this plus firm pressure is quite good for settling down wayward edges.