Imported A3 size Pdf cut up into 4 setions

I'm completely new to Illustrator.

Trying to add texts and images to an A3 size Pdf (containing a to-scale model from Sketchup) using Illustrator, without editing the model. Although the imported document looks fine, when I mouse over it, can see that it is cut into 4 equal sections by thin blue retangular lines. Meaning when I click and drag on a point on the document, that quadrant esily gets moved away from the rest of the doc, thus messing up my Sketchup model.  Can anyone help show me how to fix this please?