it seemed to me like it automatically saves the desired sheet into a new document
Well, it does exactly that, it just names it "backup of FILE_NAME".
1. Open the Workbook you're working in.
2. copy Macro into VBE and save the Workbook.
3. Tomorrow, open that same Workbook, update it, and hit Save.
4. While it's still open, run the Macro and it'll automatically save the
active Sheet to C:temp under the name "backup of FILE_NAME".
5. When you open that new copy, it only has one Sheet—the one that was active when you ran the macro.
(don't know what else you need, at least that's how I took it).
I'd be happy to find code that
copies specific Sheets and creates new Workbooks named after the sheets to a specific location
while letting me pick the file type for each Sheet... like... .xls, .pdf, .csv...
though.. pdf.. can't create... or can it?
You've got some pretty big asks here, and honestly, based on the level of expertise you're showing in these posts, it’s gonna take a lot of work and knowledge (no offense). Best bet is to find someone who actually knows VBA programming "well" and have them build a Macro for you.
The thing you're asking about copies ALL Sheets to a location and makes each file named after the Sheet, but naturally with an *.XLS extension.
On THIS link there are plenty of tutorials; check them out and see if any fit, including SaveAsPDF which has visible comments explaining what each line does. You can also find an example of saving and calling the procedure for SaveAsPDF at the link for the INVOICE in Excel.
That's all from me on this topic. Peace.