I'm reading some technical documents and have come across two spellings:
組み付ける and 組付ける
Both are used in nearly identical situations and both seem to mean "assemble" as a directive. Is there a particular reason to omit (or include) み？
This is called 送り仮名の省略. Both are the same, and usually neither is more correct.
Of course you should stick to one spelling throughout the document, so in this sense it's a small mistake. There may be a 送り仮名 convention depending on the field or the style guideline of the publisher.