I don't know of a way to redefine the origin of a complete layout... But... You can move where the exported PCB appears in the pdf sheet by: i) changing where the PCB is initially laid out with respect to the 0,0 X and Y co-ordinates at the start of the layout procedure; It may yake a few attempt to work out where to move it to. It is not a simple matter to change the X,Y co-ordinates for all items in the layout so moving is quite slow ii) select and move the whole of the final PCB (all layers at once) with respect to the 0, 0 origin X and Y co-ordinates; iii) export the layout to pdf in EasyEDA. Then open the pdf for each layer in LibreOffice (or OpenOffice) Draw (it *will* open pdfs), select the whole of the layout and move it by the same X and Y offset on each layer then export each shifted layout from Draw as a new pdf. (The page in Draw can be set to whatever size and orientation required via: >**Format > Page**)

yep, you seem right! I should have given some more tries before posting here. The exported PDF is not a "page" but a kind of. Later, when I print preview (under firefox e.g.) I can see where the PCB and its canvas is going to be placed. thanks!