OMG WTF PDF

Beware of the security flaws of the PDF format. As detailed by Julia Wolf, a senior security researcher with FireEye, in her presentation OMG WTF PDF: PDF Ambiguity and Obfuscatoin, PDFs are often used in malware attacks. See the video here and the slides here. A PDF can contain a database scanner that gets activated when the file is printed. PDFs can also be manipulated to display different content in different PDF editors or different web browsers.

PDFs can be container files, which hold files in other formats. Javascript, used to automate tasks in Acrobat is not considered to be a secure scripting language. Most anti-virus software cannot pick up on malware embedded in PDFs.

Javascript to get PDF page counts

George Johnson has posted javascript on the Adobe forum here, which you can use in Adobe Acrobat to get the page counts of multiple PDFs. Follow these steps, in Adobe Acrobat XI:

1. In the Tools console, go to Action Wizard and select 'Create New Action'.

2. Choose More Tools . . . Execute Javascript and click it into the 'Action steps to follow' area on the right. Uncheck the 'Prompt User' box, and click in 'Specify Settings'.

3. Enter this script in the Javascript Editor:

console.println(documentFileName + "\t" + numPages);

4. Name and save the action.

5. When you click on the new action in the Action Wizard menu, you will be prompted to select multiple PDF files.

6. Click start and Acrobat will start to open the files and generate a list of their page counts.

7. Close the action and go back to the Tools console. Select the JavaScript menu., and click on Javascript Debugger.

8. Select 'Console' in the View menu. A list of the PDF file names and their page counts will be displayed. You can easily copy this and parse it out in Excel.

Lookup the DPI of a PDF in Acrobat

You can check the resolution of a PDF image by using the Preflight tool. In this example, I'm working with Acrobat XI.

1. Go to Tools . . . Print Production . . . Preflight.

2. On the Profile tab, click open the PDF/X Compliance drop down menu and then choose Verify Compliance with PDF/X-1a. Then click 'Analyze'.

3. You will be moved to the 'Results' tab. Look in the Overview drop down menu. There will be a submenu for Images which will show the width and height for each page in pixels.

4. Pages of a different print sizes (8.5 x 11; 11 x 17, etc.) will have set pixel dimensions for standard resolutions such as 300 PPI. So a PDF letter size page with pixel dimensions of 2550 x 3300 will have a resolution of 300 PPI.

5. Alternatively, if you click on the magnifying glass icon on the toolbar of the Profiles tab, and then in the Image drop down menu select the option for 'Resolution of bitmap images between 300 and 600 dpi', you can Analyze the resolution of each page.

PDFs do not have a single resolution. There is a different resolution for each object in the file. The resolution of text and vector images will not change with magnification.