Regarding the original posted question - I don't think this is possible without somehow rasterizing the original PDF. In regards to the bounty, I am posting the following as an answer.
Go to http://www.frontenacmaps.ca/Html5Viewer/index.html?viewer=Public, zoom to your area of interest, add bike trails/roads etc., click on the wrenches icon in the upper-right corner of the map, on the 'Printing and Exporting tab, export the map as a GeoTIFF (GeoTIFF has location information stored in the file).
Open the exported geotiff file in QGIS 3.2 and warp/reproject it to WGS84 coordinates.
Remove the original Export.tif file. Right-click in Layers menu -> Remove Layer.
Make sure the Coordinate System is set to WGS84. Click on the coordinate system icon in the lower-right corner of QGIS, set it to WGS84.
Add a new Layout.
Set the page size.
Add a new map canvas, size it to the page, double-check coordinate system is correct, print it as a Geospatial PDF.
ADJUSTING MAP CONTENTS NOTE: Pan and zoom around in the map window with the tool pictured below. Activate tool, click in map canvas, wheel-mouse to zoom in/out, press/hold mouse button and drag mouse to pan etc. Print to PDF.
Open in Acrobat. Look for the 'Measure' Tools. Click on 'Geospatial Location Tool' -> click in the map -> you should see values in the coordinate display and be able to take distance measurements etc.