The vertical line is the limit based on current layout and printer settings. Only objects to the left of this line can be printed unless you change settings in printer setup or Layout setup... to change the size of the printable area.
The horizontal lines are the borders separating the Header layout part from the Body layout part and the body layout part from whatever layout part you have after it. A darker horizontal line without the part lable will mark the page break for this layout.
No, but they are only visible in layout mode, where you really need them to know what layout objects are in what layout part and also what portion of your layout will fit on the printed page.
The vertical line is the limit based on current layout and printer settings. Only objects to the left of this line can be printed unless you change settings in printer setup or Layout setup... to change the size of the printable area.
The horizontal lines are the borders separating the Header layout part from the Body layout part and the body layout part from whatever layout part you have after it. A darker horizontal line without the part lable will mark the page break for this layout.