# How to Overlay Two .PDFs?



## OrbitzXT (Nov 4, 2010)

I have two drawings of a building floor. One is demolition of existing items and the other is the new work and items being installed. I'd like to be able to overlap the two of them to see what distance there is between the old demo and the new work. Is this possible and if so how? I thought of converting these to autocad drawings but the program I'm using is not working for some reason.

I thought maybe it might be possible in Photoshop but I'm not very proficient with Photoshop. Any thoughts on how I can do this?


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## DanTheMan (Nov 4, 2010)

BlueBeam PDF Revu


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## OrbitzXT (Nov 4, 2010)

DanTheMan said:


> BlueBeam PDF Revu



Ah I have that installed, how do I do it with that though?


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## gvblake22 (Nov 4, 2010)

If you were ever able to get your AutoCAD working, just insert the images and rectify them so they are aligned.  Will be a lot more accurate than anything you would do within a PDF.  If you need to make real measurements on these, AutoCAD (or some kind of GIS software) would be the way to go.

If you don't need accuracy, Photoshop can in fact read directly from the PDF.  Just open each PDF separately, then select all of one, copy it, then paste it on top of the other one.  I'll do it for you if you want, just e-mail me the files.

I think what DanTheMan was referring to was THIS... (found in the BluBeam Revu Help)


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## OrbitzXT (Nov 4, 2010)

gvblake22 said:


> If you were ever able to get your AutoCAD working, just insert the images and rectify them so they are aligned.  Will be a lot more accurate than anything you would do within a PDF.  If you need to make real measurements on these, AutoCAD (or some kind of GIS software) would be the way to go.
> 
> If you don't need accuracy, Photoshop can in fact read directly from the PDF.  Just open each PDF separately, then select all of one, copy it, then paste it on top of the other one.  I'll do it for you if you want, just e-mail me the files.
> 
> I think what DanTheMan was referring to was THIS...



I have a number of files I need to do it to, so I'd like to learn how myself. But I could send you one set to try and it and send back to me to see how it looks. Should I email it to the one you PM'd to me a week or two ago?


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## gvblake22 (Nov 4, 2010)

OrbitzXT said:


> I have a number of files I need to do it to, so I'd like to learn how myself. But I could send you one set to try and it and send back to me to see how it looks. Should I email it to the one you PM'd to me a week or two ago?


Yes, that same e-mail works.  Do you need to make accurate measurements on this overlay or is it just for review purposes?  Try the process I linked to in the BuBeam Help also and see if that suits your needs.


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## OrbitzXT (Nov 4, 2010)

I'm using an out of date version of bluebeam...6.something. I believe it's a pirated version someone had downloaded and installed. This version doesn't have that Overlay feature mentioned in that link.

As for accuracy, I don't think they're doing precise measurements, but they would like it as accurate as possible to eyeball whether piping needs to be run or not. When a light fixture is removed, if the new one is going in the same place piping doesn't need to be run, but if they've shifted the location of the new fixtures around then it will be.

I've emailed you two PDFs, they're the same floor of the building but one is the demo drawing and the other is the new work drawing.


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## DanTheMan (Nov 4, 2010)

We use BlueBeam here to see what changed between two pdf's. A red area is displayed showing the differences. GV is correct it will not be very pinpoint accurate but it will show you the differences.


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## gvblake22 (Nov 4, 2010)

I just e-mailed you an 11MB file, hopefully it's not too big for your e-mail system to handle...

Oh yeah, and using illegal software at work is a very bad idea, especially when you mention it freely...

*EDIT:*
Just resaved it as a GIF (instead of JPG) and the files size went down to just under 3MB so I sent that one to you too just in case.


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## OrbitzXT (Nov 4, 2010)

gvblake22 said:


> I just e-mailed you an 11MB file, hopefully it's not too big for your e-mail system to handle...
> 
> Oh yeah, and using illegal software at work is a very bad idea, especially when you mention it freely...



The boss was so happy with what you sent me, now you must teach me how to do it =p Thanks so much Blake. Also, just out of curiosity...is it possible to make the green/red you use transparent? You did such a good job lining them up I wasn't even sure if there was demo work under some of the new work.


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## gvblake22 (Nov 4, 2010)

Yeah, I can make it rainbow colored if you want!  The extra unicorns and butterflies will cost you though... 

The process is easy in Photoshop if you know the drawings are at the same scale.  Just open the two PDF's in Photoshop individually then:

With the image you want to put on top open, activate the "Move" tool (keyboard shortcut is "v")
Left click and drag the image from the canvas up to the tab at the top and hover it over the tab for the other building image until Photoshop switches to that image.
While still holding down the left mouse button, move your pointer down onto the canvass of this new image and release the mouse button.
The two images are now on the same canvass as separate layers.  You can save this point as a PSD file.
Now, double click the top-most layer in the layers manager to bring up the blending options.
There is an option at the bottom that says "Blend If:"
Move the white slider for "This Layer" to 254 (instead of 255).  This effectively tells Photoshop to make any purely white pixel transparent.
With the move tool still active, left click and drag this top layer around and you will notice that its background is indeed transparent.
Assuming the two drawings are at the same scale, just move it around until everything lines up.It is easiest to start at opposite corners on the very outsides before worrying about anything inside.
If you want to adjust the transparency of the top image, double click it to open the layer sytle window again.
Now you can move the Opacity slider (under General Blending) to adjust that layer's transparency.  50% should work fine.
I found that saving the final image as a GIF image will keep the smallest file size.
Of course, there are other ways to do this (like using the magic wand to select all the white pixels and just deleting them), but I found this method to be the least intrusive on the original images.


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## OrbitzXT (Nov 4, 2010)

I love you Blake, I ended up PDF'ing the jpeg you sent me, then use Acrobat's "Reduce File Size" option and that got it to about 1.2MB with the same quality. I'm gonna go practice this now and finish the rest of the drawings I needed. Thanks so much again.


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## OrbitzXT (Nov 4, 2010)

I must be an idiot, I can't seem to do it. I have both files open in their own tabs, I hit "m" and my mouse turned into a crosshair. I highlighted the drawing and little moving - - - - - - - - lines are circling around what I've selected. I dragged that to the other drawing's tab, it switches over to that drawing. While still holding the mouse button I drag down to the actual drawing the the - - - - - - - box moves there, but nothing in it.

How am I noobing this up?

Edit: I figured out what I'm doing wrong, how do I color it though like you did?


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## gvblake22 (Nov 4, 2010)

Sorry about that, "m" is the shortcut for marquee select, not move.  I make that mistake all the time!  I edited my post with the correct shortcut for move, which is "v".

And yeah, I did forget to mention how I colored it! 

I just zoomed in real close on one part of the image, then selected the paint bucket fill tool and set the options to Normal mode, 100% opacity, 100 tolerance, Anti-alias yes, contiguous no.  Now change the foreground color to whatever you want and click on a line on the drawing with the paint bucket fill tool and it will color all the lines.

The other way you could do it would be to use the magic wand and select all the blank space with anti-aliasing, then delete the selection.  Now you have only the lines as real, filled pixels and you can just add a color overlay layer effect and easily change the color of the lines as many times as you want without risk of losing quality.


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## OrbitzXT (Nov 4, 2010)

gvblake22 said:


> Sorry about that, "m" is the shortcut for marquee select, not move.  I make that mistake all the time!  I edited my post with the correct shortcut for move, which is "v".
> 
> And yeah, I did forget to mention how I colored it!
> 
> ...



I'm not sure what I'm doing wrong now, I did as you mentioned while trying to color, and if I'm doing green, the entire background and everything else is turning green.


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## gvblake22 (Nov 4, 2010)

OrbitzXT said:


> I'm not sure what I'm doing wrong now, I did as you mentioned while trying to color, and if I'm doing green, the entire background and everything else is turning green.


You have to make sure your crosshair is over a black pixel.  Hold down the Alt key and roll the mouse wheel to keep zooming in until you can make out individual pixels, then try the paint bucket fill again by clicking on a black pixel.

Oh yeah, it will only look at the layer you have selected in the layers pane, so make sure you are trying to fill the same layer you have selected.


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