The one page in your document has a Group entry defining the attributes of the page (transparency) group:
/Group <<
/I true
/K true
/S /Transparency
/Type /Group
>>
The K entry is specified as
K boolean (Optional) A flag specifying whether the transparency group is a knockout group (see “Knockout Groups”). If this flag is false, later objects within the group shall be composited with earlier ones with which they overlap; if true, they shall be composited with the group’s initial backdrop and shall overwrite (“knock out”) any earlier overlapping objects. Default value: false.
As the value is true, any earlier overlapping objects (including the objects you want to be visible by transparency) are knocked out and you only see the white page background.
Using /K false
instead renders the image as desired:
Your original document (/K true
) in Adobe Reader XI:
Your document with the knockout entry disabled (/K false
) in Adobe Reader XI:
For details cf. the PDF specification ISO 32000-1
- table 30 Entries in a page object for the page dictionary Group entry;
- section 11.4.7 Page Group for a definition of the page group;
- section 11.6.6 Transparency Group XObjects for the entries of the page group dictionary.