1) render side-by-side images in a PDF
Yes. Following eskwayrd answer for Asciidoctor: how to layout two code blocks side by side? you can insert your image inside a table with only 2 columns.
[cols="a,a"]
|===
| image::foo.png[]
| image::bar.png[]
|===
I would in your case even completely hide the table
[cols="a,a", frame=none, grid=none]
|===
| image::foo.png[]
| image::bar.png[]
|===
2) center the block of images
This is currently complicated in PDF.
Well our block is now a table so we have a few options in HTML. Aligning the content with <
and >
is simple enough and works.
[cols=">a,<a", frame=none, grid=none]
|===
| image::foo.png[]
| image::bar.png[]
|===
Setting the table width to automatic and centering it also works in HTML:
[%autowidth, cols="a,a", frame=none, grid=none, role="center"]
|===
| image::foo.png[]
| image::bar.png[]
|===
These two methods however, for some reason, do not work in PDF when converting with asciidoctor-pdf
. One "solution" for PDF would be to expand your table with extra empty columns left and right and trying to adjust their width with integers.
[cols="3,1a,1a,3", frame=none, grid=none]
|===
|
| image::foo.png[]
| image::bar.png[]
|
|===