You don't need to purchase Adobe Acrobat to copy text from PDF documents. Use Adobe Reader -- a freeware program -- to open PDFs and copy their contents. If the creator of the document has protected the document in Adobe Acrobat, you can't copy the text using Reader. You can, however, use optical character recognition software to extract the text. Remember, copying and using copyrighted material may be illegal.
Unprotected PDF Documents
Launch Adobe Reader, click the "Open" button, select the PDF and click "Open" to open it. Locate the text you wish to copy and then select it using your mouse. To select everything in the document, press "Ctrl-A." To select a large portion of text, click at the beginning of the text, hold "Shift" and then click at the end. Copy the data to the clipboard by pressing "Ctrl-C" or by right-clicking the selection and selecting "Copy."
Paste the text by placing the blinking text cursor in the document where you want to insert it and pressing "Ctrl-V." You may break the formatting when pasting large swaths of text from a PDF. Although line breaks are usually preserved, margins and other text formatting -- like boldface and italics -- may be lost. The position of images may change; in some cases, you may not be able to copy the images from the PDF.
Protected PDF Documents
If the creator of the PDF document disabled content copying, you can't select and copy the text from Adobe Reader. You can use OCR software such as Microsoft OneNote, FreeOCR or SimpleOCR. Take a screenshot of the text you wish to copy and then use the OCR software to extract the text. This procedure is useful if you have forgotten the PDF password. Again, copying or using copyrighted text without permission may be illegal.