First, the general disclaimer: I’m not a lawyer and can’t offer legal advice.
Second, if you plan on creating Public Domain products, you must have this on your bookshelf: “The Public Domain: How to Find & Use Copyright-free Writings, Music, Art & More.“
An interesting source of public domain info is the FBI’s Electronic Reading Room via the Freedom of Information Act.
Since these reports were declassified and paid for US tax payer dollars, they are part of the public domain and you can bundle or package them as you wish and sell as your own products.
Mind you, some of these PDFs are extremely hard on the eyes as well as appearing convoluted due to cross outs, fading, signatures and stamps. But they are an original source of data on many popular people and topics.
One approach is to hire a competent transcriptionist/editor to clean them up for you. If you’ve edited or bundled them in a unique way, you can claim a copyright for yourself.