I don't know how to describe exactly my issue, but I'll make a try:
I am writing a document on Lyx, and I am using the module "report". I have customised the page margins but when I write paragraphs, some sentences do not obey the margin and some words are not in the same line. Graphically:

From a PDF that is created with Office there is a tool (a ruler I think) with which you can make the paragraphs in order to be all the words in the same line. For example:

How can i fix this issue?