The background color of a Microsoft Word document isn't retained when you convert to PDF. The background is white in the PDF file.
In Microsoft Word, draw a box the size of the page and fill it with the appropriate background color. Arrange the order of the elements so that the box is behind all text elements.
Note: Printer margins can trim part of the background box so that the background color does not reach the edge of the page.
Import the Word document into a page-layout application (for example, Adobe InDesign). Apply the background color you want, and then re-create the PDF file. See the documentation included with the page-layout application for instructions on importing files and applying background colors.
Adobe Acrobat Distiller uses printing information to create PDF files. Microsoft Word uses background colors for onscreen display only and does not include the background color in its printing information. Printing information in Word contains no background color information. Therefore, Acrobat Distiller cannot include a background color in a PDF file created from a Microsoft Word document. However, watermarks created with Word are included in the printing information and are retained in PDF files.
Page layout applications include background color information in their printing information; therefore Acrobat Distiller includes background colors in PDF files created from a page layout application.