How can i setwidth this table?

HTML-CSS
1

PdfPTable mainTable = new PdfPTable(medicineNews.size()+2);

2

Hello @mygmarjav, welcome to the community.
Please, the next time provide more context in the question otherwise it’s extremely difficult to help you.
With a quick Google search I assume you are using Java with the class com.lowagie.text.pdf.PdfPTable.

Please, if you haven’t already, take a look at the documentation for such a class.
The one I found is here: http://javadox.com/com.lowagie/itext/4.2.0/com/lowagie/text/pdf/PdfPTable.html

Edit: in that documentation there are various methods related to the width

Edit2: also, if it Java and the question is not html-css related, it should be moved to the correct category.