Changing my flyer into a post card, need help

I can think of a couple ways to do it, which depends on how you ultimately want to use it. For example, if you just want to print it post card sized on regular paper, you could choose to print 4 copies to a page which would, roughly speaking, give you post card size. If I remember properly, I had some post card stock paper that was a normal sized piece of paper that could easily be torn into 4 card sized pieces.

Another way would be to print it as a PDF. Then create a new Pages layout document. Insert the PDF file (Insert>Choose) which will import the PDF as a graphic file into your page. Grab a corner of the document and resize it to fit.

Somehow I doubt the shape is proportional for what you want.

The flyer is portrait, the postcard is usually landscape and the width/height ratios are widely different.

I hope you used styles to format your text.

I'd group all the text and graphics in the Flyer that you want, drag scale the group down to the size of the postcard and copy that to your postcard size document. The text will not have shrunk, but you can adjust it using your styles to a point size that will suit the new size.

If you didn't use styles on your text, just click in it and Select All (cmd a) then reduce the font size either via the toolbar or by +cmd shift -+ , then fine tune it once it all fits and is all visible.

Peter