Hi everyone!
I cannot seem to fix this issue with my footer.
Particularly, the "doccopynuevo" static string is not showing in the first page.
If I move it to the rest of the pages however (i.e. in the @page section), it does show up properly!
My simplified code:

@page {@bottom { content: counter(page);}}

@page:left {@top {content: string(doctitle) " " string(docvolume) " (" string(docissue) "): " string(docfpage) "-" string(doclpage) ", " string(docyear);}}

@page:right {@top {content:string(docshorttitle);}}

@page:first{
@top {content: string(docissn) " (en línea) " string(doctitle) " " string(docvolume) " (" string(docissue) "): " string(docfpage) "-" string(doclpage) ", " string(docyear);}
@bottom-left {content: string(doccopynuevo);}
@bottom {content: "";}
@bottom-right {content: counter(page);}
}

copy-nuevo {string-set: doccopynuevo content()}
short-title {string-set: docshorttitle content()}
journal-title {string-set: doctitle content() }
issn {string-set: docissn content()}
volume {string-set: docvolume content()}
issue {string-set: docissue content()}
fpage {string-set: docfpage content()}
lpage {string-set: doclpage content()}
year {string-set: docyear content()}

Can you could email me (mikeday@yeslogic.com) the document? Perhaps the element does not occur early enough to appear on the first page.

Sorry didn't send you the document since you pointed me in the right direction!
The element I wanted to show in the footer loaded about half way of my XML document. I moved it to the top so it would load amont the first elements and now it shows perfectly.
Thank you Mike!!! Great work