number of products per page of Collection / ProductSet in BuyButton.js (pagination)

[KnowYourMeme]

The BuyButton.js documentation http://shopify.github.io/buy-button-js/customization/ discusses pagination of a collection (which in this library is described as a ProductSet).  `pagination` can be set to `true` and the text of the `nextPageButton` can be set.

How is the number of products per page set?

[RJHallin]

I'm running into a similar issue. Were you able to come up with a solution?