# Restrict URLs and attachments in PDFs

Reader warns you any time you try to open a URL (web link) or a file attachment that uses a disallowed file type. URLs and disallowed file types (for example, EXE) are potentially dangerous because they can transfer or run programs, macros, or viruses that can damage your computer.

You can allow Reader to contact specific websites by adding those URLs to your list of allowed websites in the Trust Manager preferences. Remove any URLs you no longer want to visit. To open file attachments in Reader, you must respond to a prompt by indicating that you always allow files of that type. The attachment’s file type is then added to a list stored in the registry. If you want to restrict a file type that you permitted in the past, you can reset this list to its default settings in the Trust Manager preferences.

### Trust Manager preferences

To open the Trust Manager preferences, choose Edit > Preferences (Windows/UNIX) or Reader > Preferences (Mac OS), and select Trust Manager on the left.

Allow Opening Of Non-PDF File Attachments With External Applications

  When selected, allows file attachments to start external applications when you open the files. You must have the external applications to open the files.

Restore Default List Of Allowed And Disallowed File Attachment Types

  Removes saved settings you chose for opening attachments. For example, if you chose to always open TMP attachments when prompted, TMP appears on the list of allowed file attachment types. By clicking Restore, you remove TMP from the list.

Change Settings

  When clicked, lets you specify the default behavior for accessing the Internet from PDFs. To restrict access to only the URLs you specify, select Let Me Specify A List Of Allowed And Blocked Web Sites (the default). To allow access to all URLs, select Allow All Web Sites. To restrict access with all URLs in PDFs, select Block All Web Sites.

  To specify a list of allowed and blocked websites, type each URL in the text box, and click Allow or Block. Then specify the default behavior for Reader for websites that aren’t in the list.

  Note: If you open a protected PDF and a security warning dialog box prompts you to allow or block a URL, select Remember My Action For This Site, and the URL is added to this list.
Allow External Content

  Allows Reader to read data from stream objects in a PDF. Stream objects are URLs or file specifications identified by flags, as specified in PDF Reference Version Fifth Edition: Adobe Portable Document Format Version 1.6. Use this option if you’re a PDF developer who creates PDF files that contain streams, or if you work with these types of files.