[Plugin: Unprintable Blog] how to printable…

I’m not quite sure I understand your question.

Printing is disabled by default in all generated PDFs, as that’s the point of this plugin. If you want to generate PDF files that can be printed you could use wp-mpdf (https://www.ads-software.com/extend/plugins/wp-mpdf/).

If you want do open the generated PDF in a new window you have to insert the button code into your theme, passing true as the first parameter, e.g. <?php if(function_exists('gcp_pdf_pdfbutton')) gcp_pdf_pdfbutton(true); ?>.

If a user gets a download dialog or the PDF is opened directly inside the browser, depends on the users individual browser settings.