It is often claimed that Pope Paul VI said that Vatican II never taught infallibly so it is up for debate. This is not true (well partially – It does have to be followed and assented too). Read this excellent article on the topic from Dr. Jeff Mirus. (Linked Here)
Or Check out what Bishop Baron has to say! 5. Did Pope Paul VI say that Vatican II was ordinary, pastoral, and fallible? Linked Here
Reason and Theology on how Paul promulgated Vatican II and how people like Dr. Taylor Marshall distort what Pope Paul really said. Pope Paul VI on Dissent from Vatican II with Michael Lofton – YouTube
Take this Latin ending to Dei Verbum (as for every document)
Haec omnia et singula quae in hac Constitutione dogmatica edicta sunt, placuerunt Sacrostancti Concilii Patribus. Et Nos, Apostolica a Christo Nobis tradita potestate, illa, una cum Venerabilibus Patribus, in Spiritu Sancto approbamus, decernimus ac statuimus et quae ita synodaliter statuta sunt ad Dei gloriam promulgari iubemus.
Romae, apud S. Petrum
die XVIII mensis novembris anno MCMLXV.
Ego PAULUS Catholicae Ecclesiae Episcopus
Basically, with every document of Vatican II says with solemn words accepts the document and promulgates it (promulgari). The Pope invokes the power given him by Christ and the Holy Spirit. There should be no doubt that it must be followed.