Show what you have – Canva
Canva is your go to tool when you want to design something printed or published in the web. It provides Apps for desktops and handhelds with slightly different functions and a full blown web app.
Regardless of which tool you use – you start with a blank canvas in your desired format and get all you need to design a pleasant product. You can choose from uncountable templates, elements, stock-photos, styles, text-formats if you have a paid or sponsored subscription (or from much less with a free account) or you can upload your own elements and put it together.
Canva has some basic tools, that help you getting your poster straight, like aligning elements or colour-picking. However, it’s focus lies on ease of use and the provision of free or paid-for elements, that you can use for your product (and don’t need to right-check before publishing it).