Designs for purchase should have this option - DOWNLOAD INFORMATION on the screen with price and check-out option. This is where you will find the size of the design as well as thread colors.
This is an example - http://www.annthegran.com/Product.aspx?t=1&i=36987 Click on Download Information, then follow the instructions on the screen for a PDF that will have the information.
To enlarge what is on the screen, select file at the top left of your computer's screen. Select Print Preview. There should be a selection the states "shrink to fit" click on the arrow next to this and you should get a mini screen with page sizes smaller to larger than the normal print.
If you just want to read the screen, there should be a magnifying glass icon at the bottom right of your computer screen with a number and % sign. You can enlarge or reduce what you are viewing by clicking on this icon and making a selection.