Reply To: Fonts changing size

Possibly because the style you used in another advert or in the magazine clashes with a style, when you copy things over InDesign will use the Target document for designating styles, if no style is found, then the original style is copied.

Instead of copying and pasting the advert, perhaps you could use File>Place and just place the indesign file. If you need bleed then you have to include that in the document your bringing in under File>Document Setup.

When you place the file make sure you choose Show Import Options in the bottom left corner.

Then choose Crop to: Bleed Bounding box.

Draw a frame that is the original size of the advert, center the content, position the advert on the page, expand the frame so that it bleeds in the appropriate places.