How can I put seperate score files onto one page in the Layout?

Question

I have written some exercises in different keys. They are small files. Each of them are saved individually and cover only part of a page each but I want to lay them out on one single page. I can't work out how. Each file is in a different key. As a short term solution I tried to combine them into one file and then could not work out how to change the key signature. When I insert the #'s and b's the following notes don't move to the right. So that does not work the way I do it. Does someone have a solution, please?
Cheers,
ansu

Answer 1

Thank You, musicspirit, for your support. What you suggested I had done already, but it did not work always only sometimes. ( Like a disfunctional light switch). Maybe I missed some setting or whatever or tried too many things...or..Anyway quite a few things didn't work, I spare you the details. Meanwhile I did disk maintenance and tossed out the files and started again from scratch ( which I wanted to avoid) and everything worked out fine so far. No problems with clef change, etc.
But to make it look as if I had three songs or three separate exercises on one page I need to create a bigger space between the 3rd and 4th staves and the 6th and 7th staves. I can do this only globally, which means I manage only to increase the space between all the staves. (I hope I am not asking the wrong thing again. Manuals are not always easy for the novice.)