This repo contains a prototype algorithm for the QGIS processing framework allowing to export PDFs.

It works by taking following inputs :

• a QGIS project (current project if nothing specified)
• the layout name (the layout that you want to output)
• a list of template layers (layers from the project that are to be replaced - as a comma separated list of layers ids)
• a list of override layers (layers that will replace the template layers - must match the count and order)
• an output folder (the place where outputs will be stored)

Install as a QGIS python plugin.

This requires QGIS 3.3 including with following patch (not merged yet) : qgis/QGIS#7864

Run (or batch run) the new Export to PDF algorithm.

A sample project containing a processing model that uses the PDF exporter is included.

To use, open the project in QGIS 3.3, and run the RiskTools/Flood on buildings algorithm. Use the buildings layer and one of the rasters from the data folder as inputs. You can run it in batch.

• Issue when running the sample in batch mode because of https://issues.qgis.org/issues/19836

Prototype :

• Support other type of exports (atlas, image, ...)
• Allow to define some variables to be used in the composer (for example to display a scenario name)
• Explore using layouts files (.qpt) instead of QgsProjects, would probably require some "project builders" helper algorithms
• See if/how we can embed project files in processing models, to provide "self contained" PDF generators
• See if it's possible to use the custom widgets in the graphical modeler too
• ...

Long term:

• see if the concept can be enlarged so that Export as PDF becomes just be one of several other helper algorithms (such as append/prepend/override layer, add layouts, export PDF, etc.), which probably would require having a new QGIS project parameter type in processing
• bring this in QGIS core (as python)
• once stabilized, eventually port to C++
• ...

See discussion on the mailing list : https://lists.osgeo.org/pipermail/qgis-developer/2018-September/054424.html