@marcocevoli, Unfortunately the Pagination plugin doesn't seem to provide the current page number.
As an alternative, you could try the Uri of the page and concatenate its params with the url of the page:
<link rel="canonical" href="{{ page.url(true, true) ~ uri.params }}" />
Which will give you for example (using the Quark blog skeleton):
<link rel="canonical" href="http://localhost/grav/site-blog/page:3" />
If the uri.params contains more parameters for the page, you might need to use some Twig logic to split the params.
Note:
When blog collection is using the ordering by: date with dir: desc, I suspect SEO will be hurt instead of improved.
With that ordering, the canonical link is not static but dynamic. Each new blog item will push a number of blog items (equal to the number of paginations, or 100/limit %) to pages with increasingly higher page numbers. Hence, the 'canonical' link indexed by Google will point to the wrong page sooner or later.
Only after Google has created a fresh index of the pages, the page numbers are in sync again.
A better way might be using a canonical link based on the static value of 'year-month', or 'year' (depending on the rate of new blog items). The Archives plugin might help with that.