CIA declassification: questions and discussiom

When the CIA declassifies documents from the past, how confident can we be that these are in fact the original documents? How do we know that what they're releasing hasn't been tailored or even fabricated completely? The CIA does some wonky sneaky shit, they were functioned in this manner. So why do we take the documents that they release as the truth, I don't understand why we just collectively accept them as true. I'm talking about any documents they declassify, ones pertaining to operation northwoods, to the many ones regarding various covert regime changes like project Ajax in Iran. Any documents from the CIA... if we accept that this is a sneaky and untrustworthy organization (not harping on them, they kind of have to be) then how can we trust the documents that they give us access to?

Any thoughts? I took a month long break from Reddit and conspiracies in general ( much needed for my mental health) so I apologize if this is way off base for this subreddit. It's just something that has always bothered me. Thank you.