Render PDF from multiple HTML files

Hi all, is it possible to render a PDF from multiple input files/strings, like in [this example](https://github.com/flyingsaucerproject/flyingsaucer/blob/master/flying-saucer-examples/src/main/java/PDFRenderToMultiplePages.java) from flyingsaucer?
I had a problem with flyingsaucer, it throws something like "Page 21 was requested but document has only 20 pages"... 😞
I could set a `baseURL` for every page, on the `setDocumentFromString` method.

With openhtmltopdf I should concatenate all the HTMLs into one, right? But the base folder is not the same for all of them... 😄 In some of them it is "../styles/main.css" but in some other "../../styles/main.css" (deeper folder)