Import PDF as `Graphics`

Question

How can I import a PDF file as a Graphics object. When calling Import["filename.pdf","PDF"], Mathematica always imports the PDF as a list of Images.

If there is a way to import it as Graphics can this be set as the default?

Answer 1

As you can read on the Documentation page "Incompatible Changes since Mathematica Version 1" (thanks Alan for the link!), starting from version 12.2

The default element for Import[file,"PDF"] has been changed from Graphics to Image. Previous behavior can be accessed by specifying "PageGraphics" upon import.

There are two ways to do this:

1. Full form:

   Import["filename.pdf", {"PDF", "PageGraphics"}]
   
   ImportString[string, {"PDF", "PageGraphics"}]
   

2. Short form:

    Import["filename.pdf", "PageGraphics"]
   
    ImportString[string, "PageGraphics"]
   

Is there also a way to make this the default behavior?

I don't think there is a "legitimate" way to set the old behavior as the default behavior: changing the default behavior of built-in functions is discouraged. Just use "PageGraphics" instead of "PDF" as the second argument of Import when importing pdf files (starting from Mathematica version 12.2).

Alternatively, you can use the legacy (pre-version 12.2) syntax and specify "Pages" as the second argument - in version 12.3.1 this syntax is undocumented but still works (thanks chyanog for pointing this out!):

Import["filename.pdf", "Pages"]

ImportString[string, "Pages"]

The advantage is that you can use the same code for the new and legacy versions and avoid the usage of constructs like

ImportString[string, If[$VersionNumber >= 12.2, {"PDF", "PageGraphics"}, 
                                                {"PDF", "Pages"}]]

The disadvantage is that the support for this (now undocumented) syntax can be dropped in future versions of Mathematica.

Answer 2

An internal hack, and therefore not guaranteed to work in future, to change the default element to "PageGraphics" is as follows:

System`ConvertersDump`defaultElement[Import]["PDF"] = 
 {"PageGraphics"};
Import["ExampleData/mathematica.pdf"]
Head /@ %
(*  {Graphics}  *)

The change will persist until reset or the kernel session ends. It should be relatively safe. The default definition is

System`ConvertersDump`defaultElement[Import]["PDF"] = 
 {"PageImages"};