The document section that lists campaign officials is followed by the words, “in coordination to the extent permitted as an independent expenditure.”—a possible reference to campaign strictures imposed by campaign finance and disclosure laws.

The document was included in a package of opposition research Mr. Smith shared through an encrypted email with Matt Tait, a cybersecurity expert who once worked for British intelligence. Mr. Tait said he was approached last summer by Mr. Smith, who wanted him to help verify whether emails offered to the group by hackers came from Mrs. Clinton’s private server.

After discussing his project by phone and in emails Mr. Smith gave him a document called the “KLS research packet,” which contained articles Mr. Smith planned to use for opposition research, Mr. Tait said. The packet cover sheet is the document that listed the Trump campaign officials. Mr. Smith’s name and phone number are typed at the bottom of it.