Embedded would work but I would suggest using a Data Reference. This is designed for this use case - show me a list of objects and allow me to select on or more (multiple record). It also means the object selected is added to the field, and easier to reference in the future (than trying to take it from embedded list where checkbox and attachment are not implicitly linked).
Stealing the image from Constellation Cheat Sheet (which @Kamil_Janeczek borrowed from me) :
