I am a born again believer, but not an expert on RC doctrine. How can one tell is it is "ex cathedra"?
Here’s a list categorizing papal documents:
https://www.ewtn.com/HolySee/pontiff/categories.asp
Amoris Laetitia is an apostolic exhortation.
“...Apostolic Exhortation
A category of document similar to an Apostolic Letter, which Pope John Paul II uses to communicate to the Church the conclusions he has reached after consideration of the recommendations of a Synod of Bishops. He has also used it in other circumstances, such as to exhort religious to a deeper evangelical life...”
Amoris Laetitia doesn’t meet the requirements of an ex cathedra (from the chair) pronouncement, because Francis hasn’t officially used the full authority of his papacy to declare it, nor officially bound the whole Church to obey it.
It’s essentially a post-synod response paper. Any contradictions to the Deposit of Faith contained therein must be refuted.
How can you tell?
In one way, negatively: a pope may explicitly state that he is not writing in a binding manner.
Two examples: in Laudato Si Pope Francis said about a dozen times that he was all about "dialogue," "joining the global conversation," "Adding to the discussion" (LINK) etc. --- this is not the language of dogma.
In Amoris Laetitiae, para. 3, Pope Francis says, "I would make it clear that not all discussions of doctrinal, moral or pastoral issues need to be settled by interventions of the magisterium....Each country or region, moreover, can seek solutions better suited to its culture and sensitive to its traditions and local needs." Cardinal Raymond Burke (LINK), who is a recognized expert on the legal standing of texts, has stated that this means the document is not meant to be binding de fide.
In another way, positively: a pope *must* state explicitly that "This is binding" using a solemn form of address which uses words like "define," "declare," "command," etc. An example of this would be the kind of language used by Pope Pius XII, invoking his dogmatic authority, defining the dogma of the Assumption of Mary:
"By the authority of our Lord Jesus Christ, of the Blessed Apostles Peter and Paul, and by our own authority, we pronounce, declare, and define it to be a divinely revealed dogma: that the Immaculate Mother of God, the ever Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory".