I think the easiest way to do that would be to compress the file with a zip utility such as 7zip or powerarchiver and you can add a password to the zip file. there are other more complicated ways to hide and password protect a notepad file but I cant remember right now how to do it I will have look it up.
there also may be some software that you can use to password protect files you would just have to do a search.
A dictionary password is weak, If someone made a password like that, they obviously don't know about creating "strong" passwords. A combination of capital n lower case letters, along with alpha and numeric characters, @ least 8 characters.. should be strong enough. NO ?
Won't ANY password protection be vulnerable to these kind of password cracking programs? I mean, short of using a keyfob or thumbprint or retinal scan (all of which would seem to be overkill for securing a wordpad document unless it contaned launch codes) most encryption is going to be vulnerable to any of a dozen crackers, isn't it? If that's the case, why not use a simple method?
Then again, perhaps my ignorance is showing.
There are softwares out there to crack passwords created by compressing software, but it requires a lot of time to crack the passwords, what's more the success rate of cracking the password is low.
Here is how you can add a password to MS Word documents, File >> Save As >> Tools >> General Options >> and from there on everything is self explanatory. You can choose just to password-protect it or also password to modify it.