Canva is a design tool that helps you create for images Web or print, including blog graphics, presentations, Facebook covers, flyers, posters, and more.
Check out the video below to see more about Canva
Smore makes it easy to create online fliers and posters with slick templates and simple click and drag manipulation. Consider using smore to jazz up that old paper poster project and provide a means for all students to shine--not just those who are good at drawing, cutting and pasting.
Here's a sample smore flyer: https://www.smore.com/ja9c-the-senses
Lucidpress is an app that can be used to create presentations, brochures (including trifold), newsletter/papers, magazines, flyers, posters, etc.