Adjectives that modify a noun like "elk" get an extra 'e' at the end in most situations. It's not complicated but difficult to explain completely:
* either a "de" or "het" word used with a definite article gets the 'e': "het rode huis" "de kleine baby"
* A "de" word used with an indefinite pronoun gets the 'e': "een kleine baby" "een gezellige avond"
* A "het" word used with an indefinite pronoun gets no 'e': "een rood huis" "een lang boek"
Elke is every, enig is any. If it were "Enig pak is van mij" you would be correct.
The difference here is you purchasing EVERY suit, or ANY suit. If you purchase ANY suit you are not purchasing all of them, however if you purchase EVERY suit you would be purchasing all of the suits .