pdf generation api has changed

[ywwg]

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v1.0.0 of PDF::Reader introduced a new page-based API. There are extensive
examples showing how to use it in the README and examples directory.

For detailed documentation, check the rdocs for the PDF::Reader,
PDF::Reader::Page and PDF::Reader::ObjectHash classes.

The old API is marked as deprecated but will continue to work with no
visible warnings for now.

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