One important thing to understand in most electronic documents is that they are not a finished product. They are a set of instructions on how to operate and display them.
In this case, your document is using a fill pattern, the roses, and that leaves the door open to be "reinterpreted".
To have an acurate PDF you need to minimize the options, the interpretations. That is why you have diferent specifications of the PDF.
In this case the person making the PDF could "rasterize the fill pattern" with an apropiate resolution or generate a more standarized PDF, like an X1 or X3.
One thing you can do is "print" the document to another file using adobe reader using for example PDF creator, and export to a raster format, and in case you still need the vectors you can open them in Corel and insert the generated image in the previous step.