2. Select an entire drawing with the marquee box (hold left mouse button and drag a big box over the lines), or use 'CTRL + A' keyboard shortcut
3. CTRL + C to copy the drawing to clipboard memory
4. CTRL + P to paste the clipboard contents to your other drawing
5. Then decide one of three options (practice each mothod to see the results):
a) first method is to 'shrink' the drawing lines to fit your page. Select all lines with previous method and go EDIT > TRANSFORM > SCALE > 0.5 (50% reduction or whatever number you wish).
This makes lines and shapes shrink, so a 100mm long line now becomes 50mm long.
b) second method is to 'scale' the drawing space TOOLS > DRAWING OPTIONS > SCALE > 1:2 or 1:5 or whatever.
This makes your drawing look smaller but if you measure a line with the dimension tool it'll read the correct length. So a 100mm line will measure 100mm, it just looks smaller on your page.
c) third method is to increase your paper size FILE > PAGE SETUP > etc. By printing to a larger piece of paper you fit more of the drawing onto it.
But if you double the size of the paper and still print to regular small office paper, the SCALE of your drawing is now messed up. For example a 100mm long line on large paper will print 50mm long on small paper.