Web page mock up tools?

I need to mock up a handful of web pages for WordPress, but need a decent tool for this. Balsamic is not free anymore.

Is it worth the money?

I was considering Power Point, but the page size is not fixed, like the page on Power Point.

Then, I was considering using Word, with one file per web page. This way I could extend the page fora unique length, for each page. Is this more hassle than it's worth?

I do also have Adobe Acrobat Pro CC.

What are your suggestions?

I am not keen on dropping $89 for Balsamic, unless it would save me lots of time.

Thanks