Hi, I'm new to graphics programs and to Inkscape. I do heat transfers on T-Shirts and I thought I'd try something new. I managed
to figure out what I wanted to do and even print it. Unlike others, I don't have a printing problem. The problem I do have is sizing my
project to print full page on an 8 1/2 x 11 piece of transfer paper. It comes out about a 4.5 x 4.5 picture right now. How can I resize it
bigger. I saved it as pdf but even that doesn't fill up the paper. My printer doesn't give me any size options.
I need to print this out and need it the right size. Any help would be appreciated. Thank you.

Welcome to InkscapeForum!

Does the drawing itself need to be larger?
Edit menu > Select All. Then hold Ctrl + Shift, then grab a corner arrow with mouse and drag until it's the right size. Or Select All, then open Transform dialog > Scale.
Then depending on your printer and/or printer settings, you may or may not need to also change the page size. Keeping everything selected, go to File menu > Document Properties > Page tab > Page Size > Resize page to content > "Resize page to drawing or selection" button.

Or should the drawing stay the same size and be centered, while only the page needs to be larger?
Select All. File menu > Document Properties > Page tab > Page Size > Resize page to content, but before you click the "Resize page to drawing or selection" button, set the margins to whatever you need. Just make sure it's the same number in each Top, Bottom, Left, Right field, to be sure it's centered