PDF is not designed to be an editable format.

• Importing in LibreOffice Impress causes the PDF objects to be converted to LO objects that match as best as possible. This inevitably leads to changes because of incomplete mapping and conversion between the objects in these fundamentally different file formats. These changes may be less or more disrupting depending on the PDF.


• Importing in Gimp caused the PDF to be rendered in bitmap format. The looks are exactly the same, but an exported PDF will contain bitmap information. If vector objects were present in the original PDF, these will be lost.

Perhaps Xournal++ will suit your needs. You can add text, annotations and images to an existing PDF. The added content will be included as an additional layer, without changing the initial PDF data in any way.

Another way to add objects to an existing PDF would be to use command line tools. For example, pdftk with its stamp option allows to superimpose one PDF on another, useful for example to add page numbers, or eventually a graphic.

It is preferred, however, where possible, to work with source documents in the appropriate format for editing, and export the final version to PDF.