* Full-year revenue rises 8 pct

* Oper. margin improved to 3.7 pct from 2.9 pct

* Maintains final dividend at 2.5p

* Shares up 13 pct (Adds details)

Feb 25 (Reuters) - Fiberweb Plc (FWEB.L), a non-woven fabric maker, said on Wednesday its 2008 underlying pretax profit tripled, helped by higher margins, and expected a resilient performance this year despite the downturn.

Shares of the company jumped more than 13 percent to 28 pence on the news.

Fiberweb said the heavy restructuring undertaken in 2006 and 2007 bore fruit during 2008 and the implementation of further cost-cut actions helped improve its competitiveness.

"While the economic outlook in Fiberweb's main markets remains challenging, we expect the benefits of previous restructuring plus ongoing cost reductions and investments, together with the recent significant fall in raw material prices to mitigate the impact of the downturn," Chief Executive Daniel Dayan said in a statement.

For the year ended Dec. 31, 2008, the company said its pretax profit rose to 9 million pounds ($13.1 million) from 3 million pounds a year ago as revenue rose 8 percent to 512.8 million pounds.

Three analysts on average had expected the company to report a pretax profit before exceptional items of 7.1 million pounds on revenue of 493.3 million pounds, according to Reuters Estimates.

The company also said it maintained its 2008 final dividend at 2.5 pence. ($1=.6884 Pound) (Reporting by Usman Merchant in Bangalore; Editing by Tresa Sherin and Gopakumar Warrier)