The PDF file format is a vector format that can also hold raster images. As Inkscape is a vector editor, it can save directly to pdf by saving a copy as PDF (never save as PDF only, but always keep an SVG file, because the PDF file format supports a different set of features than the SVG file format and you may lose data in the process).
Note that for creating perfect pdf files for printing, it's better to turn to a dedicated desktop publishing software such as Scribus, which can also import SVG files.Convert your texts to paths to be sure that your PDF files will look the same across all devices.
Inkscape can also open PDF files for editing.There has been error in communication with Booktype server. Not sure right now where is the problem.
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