You can change the paper size under File>Document SetUp>Paper. As dedmin alludes, the content won't get scaled with the paper size change. If you go from A2 to A1, you'll find the content is stuffed into the upper left corner still fitting into the space of the A2 sheet. You can only set one sheet size per LayOut file. If you need more than one sheet size you'll need to split it into more than one LO project. You can combine PDFs if needed in Acrobat or some other applications.