Everybody drafts from the last one. The danger is not the copying. It is the one line you forgot was specific to the last customer.
Here is how almost every recurring document in a small business actually gets made. You open the last one. You change the name, the date, the numbers. You skim for anything else that looks specific. You send it.
That works nine times. The tenth time, a clause that was negotiated for one particular customer rides along into a new agreement. Or last quarter's figure survives into this quarter's report. Or a name you forgot to change appears on page three.
Nobody was careless. The process itself is the hazard: the document you are copying is simultaneously your template and someone else's finished, customized work. Those two things should never have been the same file.
Three things that get collapsed into one
The trusted base
Your structure, your standard language, your formatting. Approved once, deliberately, and changed only on purpose. Not last month's output.
This instance's facts
The name, the dates, the amounts, the specifics. Kept explicitly separate so there is no ambiguity about what is supposed to change every time.
Drafting instructions
The rules that are currently in your head. Which sections are optional. What triggers the extra paragraph. What must never be omitted. Written down once, applied consistently after that.
Separate those three and the failure mode disappears structurally rather than through vigilance. A stale value cannot survive, because the base document never contained it.
What review looks like when it works
Reviewing a document you did not write is hard, because you have to read every line to find the two that changed. Reviewing a document assembled from a known base and named facts is easy: you check the facts, confirm the optional sections were chosen correctly, and read the one part that is genuinely new.
The time saved is real, but the reason to do it is the class of mistake that becomes structurally impossible.
Which documents deserve this
The ones you produce repeatedly where a wrong detail costs real money or credibility. Proposals. Agreements. Recurring client reports. Anything with numbers in it that a customer will act on.
One-off documents do not need this. The setup only pays back on repetition.