Just a question here (I have no doubt that the bc is authentic): Did the White House have to scan the document and create a PDF to put it on the web? Could they have just put up a photograph? Or would a digital photograph be the equivalent of a scan? Suppose they took a photograph with a film camera? Could something have been put up without creating all these "layering" issues?
Just to expand a bit on what Jay said ... it's not surprising that someone in the government would scan a document into PDF format rather than as a simple image. The PDF format is commonly used in government and business settings because it offers advantages over pure image formats like JPG, GIF, or TIF.
PDFs are designed to capture both the information and the appearance of documents. A document printed or viewed from a PDF file should look almost the same wherever it is printed or displayed.
Another advantage is that the textural information from the document is searchable when it is stored as a PDF. If you scanned a receipt into a JPG image file, for example, you wouldn't be able to search for it in your computer by entering some of the text displayed on the reciept. PDF scanning software, on the other hand, tries to interpret the content of the document as it is scanned. So, if you scanned a receipt using PDF software, you should be able to find it using the name of the store or other information displayed on receipt.
The PDF file format is designed to support both of the things I just described - displaying the document as it originally looked and capturing information from it as text. Plus, the scanning software tries to keep the file size as small as possible. To meet these goals the document is scanned into multiple layers or objects or whatever.
At the lowest level, the scanning software stores as much of the information from the document as it can as text. It uses OCR technology to figure out what letters are displayed and what font is used. It stores this information as text because test takes less memory than storing images and text can be easily indexed for searching.
On top of the captured text, the PDF file contains graphics - images representing non-text parts of the documents; text that it couldn't decipher; and images of some of the text that it did decipher but wouldn't be easy to reproduce for printing or display.
PDF viewing or printing software takes the text, renders it using embedded fonts and other information, then adds the stuff captured as images to reproduce the original document.
The PDF format (and others like it) are really cool because they allow exisitng printed documents to be stored digitally, indexed, and searched then displayed or printed without losing the look of the original document.
-- Roger