High Resolution Monograms

I haven't been on this site in so long. I think I could get addicted again. Anyways, I am currently helping my friend with her wedding and making monograms for her. My question is, how do I save the monograms so that they are high resolution and she can resize them without them being blurry. I do not have photoshop. I have been making them on powerpoint and word. Any help would be greatly appreciated. I am not even sure if I can save them with high resolution without using photoshop.

TIA