The verb abbinare is commonly followed by "a"; it is also possible to use it followed by "con" - the meaning is the same. In your phrase:
Abbinate le foto numerate a queste parole
the preposition "a" is chosen probably for two reasons: 1) because it is more common, and 2) because "con" can be ambiguous because:
Abbinate le foto numerate con queste parole
would mean that the photos are numerated by "queste parole". It is true that "queste parole" (these words) does not mean "questi numeri" (these numbers), but: 1) the phrase "queste parole" could be followed by a list of words like "uno" "due" "tre"... (words expressing numbers); 2) to distinguish correctly the usage of "con" in this phrase, in order to connect it to "abbinate", one should use semantics.
The preposition "a" is used, among other things, to express a movement or an orientation; the preposition "con" expresses instead, among other things, the "agent" performing (or helping) the action: "mangio la mela con le mani" (I eat the apple using my hands).
"con" expresses also a coupling (for example "io con te" - me together with you), so it is not wrong to use it with "abbinare"; for example, one can say "metti quelle scarpe, si abbinano con la tua cintura" (wear those shoes, they mate to your belt). And note that the sentence "mangio la mela con le mani" has a little ambiguity, because it could (ok, hardly) mean "I eat the apple together with my hands)", as in "mangio la mela col pane" (I eat apple and bread).