Unfortunately currently there is no easy way to do that.

The horizontal margins (insets) impact HTML-to-PDF scale factor:
scale = (pageFormat.width – insets.left – insets.right) / htmlWidth
so a lot of flexibility in page-specific margins definitions could cause undesired drawbacks.

However a swap of insets.left and insets.right depending on odd or even page seems to be doable and harmless. And I guess the limited feature would be sufficient for your case.

We are ready to add it to our API. The implementation priority would depend on the PD4ML license type you own / are going to order. Please contact PD4ML support by email.