The correct answer to this open question is the following.
A seminal document is that kind of document that provides new or innovative ideas or concepts that transcends the test of time. It could be scientific information or historical information. In the case of historical documents, it could be documents, papers, speeches, acts or decrees that were so important that change the historical moment in a country or shaped the nation.
An editorial is the opinion of the newspaper, the TV network or any news broadcasting system on any topic of interest. The editorial is part of journalism in the opinion genres that mark the posture of the Editors on an important topic. It is subjective. That is why an editorial is not considered a seminal document.