Whether or not you can extract text from a PDF document depends on how it was created.
For a normal PDF document in which fonts are embedded or standard fonts are used you can use the Text Select Tool in Adobe Acrobat Reader to copy chunks of text. You will invariably lose the formating information though. So if you're trying to copy a table you'll end up with the cell contents in lines with spaces as a separators. Could possibly use the Text > Table function in Word to get things back in order.
However, often when a document have been scanned and the image has been used to create the PDF document without the use of OCR (character recognition) software, you'll find that you actually have an image of the text rather than the text itself. So Text Select won't be possible. You could perhaps use the Graphics Select Tool to copy an image of the table then use OCR software to try and extract the text from the image file.