Artefact-free Image Upscaling

[XByrne]

Thanks to all! PDF-XChange Editor certainly reads well on their website. And the whole 'portableapps' world is new to me.

I'll let you know how I'm getting on as I move along with this project.

[XByrne]

Thanks to all for suggestions so far.

I'm trying various PDF combining programs.

Having exported three test PDF files with CMYK 300dpi images, embedded fonts, crop marks and in PDF/X4 format and imported them into my PDF combining program, I now add correct page numbers, content page and I'm all set to export the new, combined PDF file...

Do I just export as PDF/X4 again?
If I choose embed profile CMYK for images, am I adding a profile onto a profile?
If I again specify 300dpi for images, am I recompressing the images again?

Finally, and this question should really be put before I import my PDF files into the PDF combiner...
I want to keep my CMYK 300dpi files untouched on import. Can I do that?

This is the last part of the workflow and I'm nearly there, so I appreciate any suggestions for this last part.

Seamus