Embedded scale/units in PDF exports... missing feature?

[arq_42]

I've seen some forum threads discussing something similar, but they always focus on the print scale, and that's NOT what it's about. I have found what I am referring to in this Invertor Forum , but they do not provide a solution.

When you print to PDF from AutoCAD, regardless of the driver you use (DGWtoPDF, PDF24, Acrobat, etc.), the files come out with a hidden feature that I haven't been able to find how to enable/disable: you can get the actual measurements in the PDF viewer without setting the scale, and it gives you the actual measurements of the building.

Bluebeam:

Acrobat:

However, Revit exports to PDF (again, regardless of whether you use OOB, PDF24, etc.), and when you use the measure tool, it's as if you were measuring on paper with a ruler.

You can change the scale, but by hand.

Bluebeam:

Acrobat:

This embedded scale feature can be clearly seen both in Acrobat's 2D measurement options ("Use scale and units from document (When Present") and in BlueBeam Revu's "Use Embedded Scale" tools.

In fact, BlueBeam can even highlight AutoCAD viewports.

AutoCAD Exported PDF (Highlight each Viewport AND measure each one with its own scale):

Revit Exported PDF (Doesn't highlight anything)

And yes, I know many of you will say, "Why do I want to measure in PDF?" "It's not even close to the best tool for that"... etc.

BUT, both my client and the city council always use that tool and require it.

Is there a way to enable this in Revit, or do we have to make a request that autodesk will ignore?

[RSomppi]

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@arq_42 wrote:

do we have to make a request that autodesk will ignore?

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Why so negative?

This may not be possible in Revit since it automatically switches to raster printing for some things.

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@arq_42 wrote:

BUT, both my client and the city council always use that tool and require it.

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Then they should know how to make their PDF readers measure to scale. Until that happens and they remove the requirement, you may have to export to AutoCAD and make the PDFs with AutoCAD.

[fitzmorrispr]

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This may not be possible in Revit since it automatically switches to raster printing for some things.

I don't know how Revit handles exports behind the scenes, but if the raster is accurately scaled to the page then it is absolutely possible to embed the scale.

PDF allows for a Page dictionary object to contain one or more VP (viewport) dictionary objects, each of which specifies its BBox (bounding box) rectangle, and optionally, a Name string and a Measure dictionary object. The Measure dictionary can specify an overall scale factor, separate x and y scale factors, unit conversions for distances, areas, angles and slopes, and the canonical origin of the viewport. Ref: PDF32000_2008.pdf, section 12.9

All of this can actually be stored as plain text inside the PDF file, separate from any image data present on the page. The viewer software is responsible for scaling and positioning any rasters and viewports accurately, which they generally do very well.

Measuring will of course be less accurate with a raster than a collection of lines, if only because Acrobat's measuring tool's snapping feature cannot detect endpoints/intersections/midpoints/lines on a raster, but it does allow the user to pick arbitrary points, and this can be done at almost any zoom level, so in practice the accuracy is up to the user

In theory, the aforementioned VP and Measure dictionary objects could be manually added to a PDF Page by the user, but the PDF file's nature as a hybrid of binary and text data means that manual edits can break it, and that some or all of the objects might be encoded instead of plain text, so it's not trivial. And most visual editors don't expose the functionality. You'd probably have to use a tool like qpdf if you wanted to do it.