I have not got Elements 8, but the following should work.
Do a File - New and choose a A4.
Open a new image, and place it so that part of the blank sheet is visible.
Choose the Move tool (V on the keyboard) or top of the toolbar.
Click and hold on the new image and drag on to the Blank A4. Let go of the mouse and the image is on the new sheet. With the move tool you can put to picture anywhere you want.
Ensure that the box on the top of the screen "show bounding box" or "show transform control" is ticked.
By moving the mouse over one of the corners, and holding down the shift key, the size of the picture can now be changed without altering the proportions. (if you do not hold down the shift key, the picture becomes distorted)
Repeat for other pictures. If the box "auto select" is ticked, clicking on a picture will automatically select that picture.
I do not know if Elements 8 has full control of rulers and guides, but "View-rulers" or guides will give you rulers along the edge of the sheet for sizing pictures. Setting guides can help for your pictures to "snap to".
Right clicking on a ruler gives you the option to select mm, inches, cm , pixels or whatever.
When finished, use Layers-flatten image and than you can print.
Hope this helps.