Here is a quick guide that should help you resizing the file if it is too big, or too small.
Step 1: Open the photo/scan.
Step 2: Click Tools on the top of the screen
Step 3: Click Adjust size
Step 4: Select the Resolution and adjust as is appropriate up of down if the file is too small or too large. It will state beneath it the resulting size of the file created by the change you have entered.
Step 5: Press OK and save
Step 1: Open the photo/scan in Paint
Step 2: Click on Resize and Skew
Step 3: Enter the appropriate percentages for the Horizontal and Vertical to increase or decrease the picture size.
Step 4: Save as a Jpeg file.
Alternatively, in Windows:
Step 1: Open the photo/scan in Windows Word.
Step 2: Adjust the size by dragging the image corners.
Step 3: Copy the new image.
Step 4: Paste the new image into paint.
Step 5: Save as Jpeg file.