Exporting to PDF from ArcGIS Pro is producing large file sizes
Hi Monika,
Thanks for sharing the map packages (note to other readers of this thread: you must be logged in to see and download those!).
I now had a look at the map packages, and exported them to 100,600,1200 and 3600 dpi PDFs in ArcMap, and 100 and 3600 dpi in Pro.
Look at this first image:
The first 4 listed files without "_Pro_" in the filename, are the ArcMap export. Notice that with increasing output dpi, the file size also increases. Now look at the last two files from Pro, and notice that although there is a size increase, it is relatively small.
Why is this?
There is a fundamental difference in how Pro and ArcMap handle the vector PDF export: in Pro, almost all the coordinate information of the original polygons and lines, will be retained in the PDF output, even if you set a low dpi output resolution. Pro will always (attempt to) generate high quality vector output. This means that linework of polygons and polylines will remain smooth - at least if the dataset is suitable for the scale at which it is being used - and things like text halos will be of high quality in the PDF output, even when zoomed in at e.g. 800% percent in Adobe Reader.
In essence, although this is not entirely true, the Resolution (DPI) as displayed in the Pro export dialog, is meaningless if you only export ***100% vector*** PDFs!!! Note: with raster or image layers in your map document, DPI is meaningful and will strongly impact output file size and quality.
ArcMap on the other hand, due to using a different display pipeline, has a dependency between the dpi setting and the vector output quality: the lower the dpi, the coarser the vector output in the output PDF!
Look at the images below, which are 800% zoomed in screenshots from the export as seen in Adobe Reader. First look at the top two images, which are 100dpi output from ArcMap and Pro respectively. Notice how, zoomed in at 800% in Adobe Reader, the ArcMap output looks "blocky", almost rasterized. Even though it looks rasterized, it is still vector data, but the coordinates of the vectors have been snapped to 100dpi coordinate grid. This causes the "blocky" appearance. This is the way how ArcMap handles this, and is a direct consequence of the different display pipeline in ArcMap versus Pro.
Now look at the second ArcGIS Pro image, also 100dpi output: notice the detailed - but jagged - linework? This is caused because your data is at very high true coordinate resolution compared to the scale at which you are trying to display it. Since Pro will output nearly all coordinates, the final file size is big as well (see the first screenshot above), but this is direct consequence of using highly detailed apparently "local" data displayed at "country" scale in the layout.
Now look at the subsequent images from ArcMap at 600, 1200 and 3600 dpi output. Notice that with increasing resolution, the images start to look more and more like the Pro export: lines are more detailed, but start to look jagged due to an abundance of detail in the original datasets. Also notice the increasing file size because of this, going from a mere 0.4MB at 100dpi, up to 7.6MB at 3600dpi.
Now how to solve this?
There are two aspects to this:
- Clearly, the data you are using is far more detailed than is needed for a country overview. To get better quality output in ArcGIS Pro with smaller output PDF file sizes, without the jagged over-detailed linework, you should generalize the datasets using e.g. the Simplify Polygon tool.
- A second aspect is that it would be good if ESRI allowed some form of target vector output resolution for Pro, automatically mildly generalizing or simplifying the vector output if the underlying datasets are of a higher resolution than is realistically necessary for high quality output. In ArcMap, this functionality was a direct consequence of the used Windows GDI display pipeline. For Pro, using a different display pipeline, this probably requires another solution.
