An ACP fileis a single file that bundles together the meta-data and content files for the information to be transported.it contains an xml file that describle repository nodes metadata and their association(reference).During importting the acp file when metting reference element(a node Na is referencing another node Nb),import engine will first search the referenced node Nb using xpath language.XPath language need Invalid characters to be encoded in the form "_xhhhh_" where the four digits represent the hex encoding of the character. For example, the space character, "a b", would get encoded to "a_x0020_b".So your path cm:documentLibrary/cm:uploads/cm:_x0032_014/cm:_x0030_6/cm:_x0031_7/cm:_x0031_1-30-48–user/cm:_x0036_6.pdf
is the encoded one. It seems this node dose not exist ,you can check if it exists using node browser. If it dose not exist ,you can try to create it using web client and reimport your acp.