I have one file and contains:
file2.txt
PRIMERB
PrinceValiant
Priory
PRISTINA
embossed
heavy
incised
light
Outline
ribbon
Instead of finding some way of automating this, I think it'll be easier for you to just copy & paste...
But that purely depends on how many rows of text you got in those text files. If they contain less then 50 lines, I suggest you just copy (or cut) and paste.
I wouldn't know any way to automate that in Notepad++ anyway.
Edit:
After your request I wrote a quick PHP script that takes the lines from 'file1.txt' and 'file2.txt' and combines it to 'file3.txt'
Now I would like to help you best I can, but I cannot access my own domain at this time, and I have not yet wrote something for you to upload your own files to it.
You can run this your own by downloading the latest USBWebserver
1. Extract the files from the .zip you downloaded from the USBWebserver website.
2. Go to the just extracted 'root' folder.
3. Delete everything inside that 'root' folder.
4. Copy the code above and save it as 'index.php' inside the 'root' folder (you can do this with notepad++ too).
5. Move your 'file1.txt' and 'file2.txt' to the same 'root' folder.
6. Go up one folder and execute 'usbwebserver.exe'.
7. Click on 'localhost' when the window pops up.
8. If you get the message: "Writing to file 'file3.txt' was successfull." you should now have 'file3.txt' in that 'root' folder.