You cannot change the berth printed on a confirmed ticket. IRCTC has no facility for it, and cancelling to rebook usually costs you the confirmation.
So the practical question is not how to edit the ticket, but how to end up sleeping in a lower berth anyway. Two things do that.
Option 1: a vacant berth from the TTE
Once the chart is prepared, no-shows and late cancellations leave real gaps, and the TTE can allot them. Senior citizens holding an upper or middle berth get priority for any vacant lower berth.
Worth asking on every journey, because it costs nothing. Just do not count on it: a full train has no gaps to give.
Option 2: swap with someone who wants your upper berth
This is the one that works on a full train, because it does not need an empty berth — only a willing person.
And willing people are common. An upper berth means sleeping whenever you want rather than waiting for the lower berth to be freed up, no one sitting on your bed through the afternoon, and no one brushing past your feet all night. A fair number of travellers pick it on purpose.
So the trade is genuinely even. You want to stop climbing; they want to be left alone. Neither of you is doing the other a favour so much as fixing a mismatch.
What changes on your ticket: nothing
This is worth stating plainly, because it is the part people worry about. Your PNR is unchanged. Your name, coach and berth number on the chart are unchanged. No refund, no fee, no paperwork.
The two of you have simply agreed where to sleep. If the TTE asks while checking tickets, say you have exchanged with the passenger opposite by mutual agreement — that is normally all it takes.
Finding the person before you board
The traditional method is to board and ask your neighbours, which reaches roughly six people and only once you are already on the train. If none of them is interested, you climb.
BerthSwap exists for exactly this gap: post that you have an upper berth and want a lower, and see everyone on your train and date who wants the opposite — before the journey, so it is settled by the time you step on.
Common questions
Can I change my upper berth to a lower berth after booking?
Not on the ticket itself — IRCTC has no option to change a confirmed berth. You can ask the TTE to allot a vacant lower berth on board, or swap with a co-passenger who prefers an upper berth.
Why would anyone give up a lower berth for an upper one?
Many travellers prefer the upper berth. You can lie down at any time instead of waiting for the lower berth to be vacated, nobody sits on your bed during the day, and there is no foot traffic past you at night.
Does swapping berths change my PNR?
No. A swap is a private arrangement between two passengers about where they sleep. Your PNR, name, coach and berth number on the chart all stay exactly as booked.
Railway rules change from time to time and a lot is left to the discretion of on-board staff. Treat this as a traveller's guide, not an official ruling — check with Indian Railways or IRCTC if something matters to your journey.