How to export a PDF with pages as jpg or tiff, can not be modified by any editor (such as Illustrator or CorelDraw).

As far as I'm aware, other than password protecting the PDF (which can easily be circumvented), only raster-based PDFs would prevent easy editing of otherwise easily edited content such as text or vector objects.

Of course, even raster-based PDFs can be opened in an image editor such as Photoshop and manipulated as images. But in general editing raster-based PDFs can be much more of a chore than editing customary raster+vector based PDFs which InDesign and Illustrator both generate.

Simply, save or export the pages as jpg or tiff, then build a PDF from those images.

You can drag a group of jpgs to Acrobat to generate a PDF. Or use File > Create > Combine Files into Single PDF... within Acrobat Pro to generate a PDF from multiple images/files.

There's no way, which I'm aware of, from within Illustrator or InDesign to generate a raster image only based PDF upon output. Unless, of course, your document is entirely raster based.

Within Illustrator, you could select all and choose Object > Rasterize then save as a PDF. (Then undo to reverse the rasterization.)