You can make print on a PDF document appear larger by manually scaling the pages. To do so using Adobe Reader 9 or an earlier version, go to File, click Print, click Page Scaling and select Tile All Pages. When the Tile Scale window opens, type the percentage you want to magnify the document. To refresh the preview, click any other option. If you're satisfied with the size of the print, click Print or OK.
If the document is online, for example in your email, you can use Google Docs to increase the size of the font. First, log in to your Gmail account using your email address and password. Next, go to the location of the document and open it. Once the document opens, use your mouse to select the text you want to enlarge. If you wish to enlarge the whole document, right-click anywhere inside the document, go to Edit, and click Select All.
Afterwards, go to the toolbar and click the Font Size button, which is an icon with a number embedded onto it. When a drop-down menu with values opens, select a value greater than the current font size. Finally, click the Print button to see the print preview and to access the appropriate printing options.