To download all tabs of a Google Doc as one PDF, click File > Download > PDF document (.pdf), switch the tab option from Current Tab to All Tabs, and click Export. Google Docs saves every tab, in tab order, as a single PDF. File > Print > Print all tabs works too.
Google Docs has no way to download or print a Doc with its comments as a PDF: File > Download > PDF and File > Print leave the comments out. To keep them, download the Doc as Microsoft Word (.docx), open it in Word, and print or save a PDF with Print Markup turned on.
To convert Word to PDF, open the document and choose File > Save As (or File > Export > Create PDF/XPS), select PDF as the file type, and click Save. In Word for the web, use File > Export > Download as PDF. On a Mac, choose File > Save As and set File Format to PDF.
To insert a PDF into LaTeX, load pdfpages with \usepackage{pdfpages} and use \includepdf[pages=-]{file.pdf} to insert every page as a full page; pages={1-3} takes a range. To place one PDF page as a figure inside your text, use \includegraphics[page=2,width=\textwidth]{file.pdf} from the graphicx package.
