Best digital design platform to offer various page size options?

[OneLittleBearDesigns]

Hi all, I have a digital download shop but up until now I've only needed to offer 8 1/2 x 11 files, so I have been creating all my designs in Word and exporting them to a PDF. It's just what I'm most comfortable/familiar with. Unfortunately using Word, it doesn't rescale things when you change paper size. I'm currently working on a more poster-size design, and need to be able to upload different size options. What other platforms could I create in to accomplish this? I was trying avoid paying for something, but I may have to bite the bullet unless there's a way to save a PDF in different page sizes? Thanks in advance!

[DesertChains]

Microsoft Word is not a desktop publishing program. Use a program made for this purpose, such as Indesign. You will able to create any size you need. However, I don’t know of any publishing program that will scale the contents when you resize the page. (Photoshop will do it if you apply all content to a single layer, and then resize the layer, but that will cause distortion.)

[givemeacrown]

@OneLittleBearDesigns - If the ratio is the same but you just need different sizes you can set up the page in Word at the biggest size. You can then "Print to PDF" and specify the size of exported file to be whatever sizes you need.  I'm in Australia and use ISO sizes for documents so for instance I could create a document that's A2 size, then "Print to PDF" at A3 and A4 because they're the same ratio.

You will need to be cautious of things like font size - make sure the fonts are large enough on the large version that when it's shrunk down to the smallest it is still legible. 

If the designs are different ratios then you may need to create a separate file for each size. Using programs like Illustrator and InDesign allow you to work in vector graphics which make the scaling easier but the software has fees and the learning curve can be steep.

Canva or Adobe Express have free versions with some useful functionality but the best bits require subscription. e.g. In the free version you can create a large design in Canva and then create a separate smaller version to add the large one in to the smaller one and re-arrange/adjust the elements so it fits the smaller size.