The sentence begins, "We hold these truths to be self-evident, that all men are created equal" and goes on to say all men are endowed with unalienable rights including "life, liberty and the pursuit of happiness." The document then goes on to say, "That to secure these rights governments are instituted among men, deriving their just powers from the consent of the governed..."
The National Archives version of the document puts a period after happiness, something Allen says was not in the original document and changes the meaning of the second sentence. The sentence is meant to move from the value of individual rights to the importance of government protecting those rights, Allen says. She says this is lost with the addition of the period.
In her study, Allen says the should-be large sentence forms a syllogism, or logical argument based on multiple propositions, and its sections were meant to build upon each other and be parts of the same collective thought. (Via Institute for Advanced Study) She says this style of writing is common in 18th-century literature and the typo obscures "a diverse textual tradition." (Via CAN TV)