Export Pages document to PDF/X-1a:2001?

The native document format in OS X is PDF, and is based on PDF v1.3. Although PDF/X-1a:2001 was based on PDF v1.3, and PDF/X-1a:2003 is based on PDF v1.4, Apple implemented neither standard in their PDF frameworks, as the underlying operating system changes would be extensive with exorbitant Adobe royalties. You will have to seek third-party application support to open a Pages exported PDF, and then re-export it to PDF/X-1a.

Current third-party applications that support the PDF/X-1a standard have moved on to the newer PDF/X-1a:2003 standard. One application is the $50USD Affinity Designer that can open a PDF exported from Pages, and export to PDF/X-1a:2003 PDF standard. It also supports PDF/X-3 and PDF/X-4 standards for export.

When you open this converted PDF in Adobe Acrobat Reader DC, it will have a thin green border around the document view to let you know it is PDF/X-1a content, and the following also appears in the Reader PDF properties:

Affinity offers a fully functional trial of Designer at the bottom of their landing page of their website. Just follow the Serif Labs Web Site link from the Mac App Store Affinity page above. When you first open the exported Pages PDF, the Affinity Designer panel will have one preselection. Uncheck that, and proceed.

I own both Affinity Designer and Photo products. I receive no compensation or other consideration from Serif for product recommendation.

Apple has only one version of export to PDF.

Why they chose the fairly useless one, we do not know.

ColorSync has some filters you might want to fiddle with and possibly add as workflows to the Print dialogue where you can create PDFs from them. Good luck with that however, I fiddled with them for years and it never got me anywhere.

Peter