Poppler does not handle Ink Annotations without InkList and an AP stream instead.
The following example, the ink annotations on page one are not rendered by poppler. draft-dkg-openpgp-abuse-resistant-keystore-03-Exported.pdf
While the annotations are not strictly conforming to the PDF spec (according to Table 182 in PDF32000 Book, InkList is a required entry and these ink annotations don't have this, but they do have an AP entry, and the same table says that AP takes precedence over the InkList and BS entries) Currently poppler rejects Ink annotations without InkList entries, which results in these annotations not being rendered. Since these annotations do have an AP we could safely ignore the fact they dont' have an InkList and use the AP to render them, so we need to implement AP rendering on these annotations.