Keeping client data on the device solves a lot. It leaves one problem: there is a single copy, and it is in your bag.
The advice in an earlier post here was to lean on the device’s own backup routine. That advice was thin. You cannot hand a whole-device backup to a new iPad on a Tuesday morning, cracked screen on the desk, client waiting. You also cannot keep a copy of it somewhere away from the device it came from.
So: one file, holding everything.
One file, and what is in it
Settings has a Backup and Restore section. Create Backup writes a single archive and hands it to the share sheet, so you decide where it goes.

Inside that archive is a dump of your clients, templates, and signed forms. Alongside it sits every file those records point at: template PDFs, signed PDFs, and any attachments on a client. That last part matters, because a backup carrying the database but not the PDFs would restore a list of forms that all failed to open.

The file is named after the date it was made.
It stores your data, not a copy of the database
The straightforward way to build a backup is to copy the app’s database file. It works until the app updates and changes the shape of that database, at which point old backups either need migrating or stop restoring. That is how backups quietly rot.
Instead, a backup here is a readable dump of the records themselves, written out and then read back in through whatever version of the app is doing the restoring. A file made on an older version restores into a newer one: the new version reads the records and saves them the same way it saves anything else. So a backup from six months ago is still a backup.
Restoring replaces, it does not merge
Restore from Backup asks you to confirm before it does anything, and the confirmation says what it does: it replaces all current clients, templates, and forms with the contents of the backup, and it cannot be undone.
Restoring is for a new or wiped device, or for rolling a device back to a known state. It is not a way to combine two iPads that have both been collecting forms. If you restore a Monday backup onto a device that has been signing forms all week, that week is gone.
A restore that fails partway will not leave you stranded. It checks the archive first. Then it copies the new PDFs in, which is safe because their names cannot collide with what is already there. Last, it swaps the records over in one go. If anything breaks before that swap, the copied files are removed again and your existing data is exactly as it was. There is no state where half a backup has landed.
A restore can also finish with warnings rather than failing outright. The usual one is a PDF whose contents no longer match what the archive recorded for it, which normally means the file was damaged in transit. You get told which file, and the rest of the restore completes. Refusing everything because one file is off would be worse.
Where to keep the file
A backup that only lives on the iPad is not a backup. Once the share sheet is open, pick the option that means the file survives losing the device: iCloud Drive, a folder on a computer, an external drive, or AirDrop to a second device in the practice.
A backup contains all of your client data. If you run everything on the device because client information should not sit on a vendor’s server, apply the same rule to where the backup goes. A practice-controlled computer or an encrypted external drive keeps that property; a random cloud folder does not. It is one file, not a sync process, so you decide where it lands each time.
Two habits. Make a backup before restoring one, so the state you are leaving is recoverable. And make one after any session where you set up templates, since re-placing fields on a form is the slowest thing to redo.

Backup and restore is part of Pro.
The short version
Create a backup in Settings and you get a single file holding every client, template, signed form, PDF, and attachment. It stores your records rather than a database file, so old backups still restore after app updates. Restoring replaces everything on the device and says so before it starts, so use it for a new or wiped iPad rather than to merge two of them. Keep the file somewhere that survives losing the device, and somewhere you are willing to have client data.
InPersonForms is on the App Store for iPhone and iPad.