Short Answer: Do NOT Copy and Paste Any Paragraphs!
As with your visitors, search engines do not want to read the same redundant information over again. The most important rule--far more critical than number of repetitions--is:
To write for your visitors to keep them engaged and informed!
If you follow that, then you will be most probable to have the right amount of repetitions.
However, to go in more technical detail and provide some directions:
- Make sure each module excerpt on the main page is indeed a summary of what is to come on the module page itself.
- Link the most relevant string of words in 8each module paragraph on the main page* to the respective module page.
- Just as with the module summaries on the main page, you may write a few sentences on each module page about the whole suite (represented on the main page) and use a phrase in that paragraph to link to the main page. This will be slightly different on each module page, since each module relates to the whole at least slightly differently.
- If applicable to your situation, write about the relationship of one module to the other and link the sub-pages appropriately.
Doing the above will help ensure a fluid experience when educating your visitor on your modules, as well as a great highly-relevant internal link and content structure within the 5-page website.
Of course remember to handle your title, Header and other tags appropriately with seo-friendly techniques as well.