I imported a document which contains muliple A4 files merged together. 

I want to Auto Trace them at once. 

How can I do It?

There´s nothing to autotrace because there are only vector data in your file.

But they are separated into different A4 pages.

How can I merge them in an easy, quick way?

Can you obtain a PDF version of this pattern? 
Glanced at the SVG imported design and it is a disaster. Switch to Outline view mode to see what I am seeing. None of those pages came in as A4 size. Could be the document scale or DPI is wrong on the export. Who knows? 

Original pdf file is this.

Normally all the A4 pages do not fit in A0 file.

You need to spread the drawings into probably 3 A0 files.

But you have to keep the integrity of the each vector drawing. (I mean Front Body Pattern, Back Body Pattern, Belt Pattern, Arm Pattern)

You can not split the for example some of the Front Body Pattern is on the Page 1 the rest of It on the Page 2.

So what do you recommend?

I'm not sure what to tell you what to do. I imported the PDF into Inkscape and this is what I see in Outline mode. 

The attached file is the best I can do. It looks scaled properly.

Ok. You rescaled the preview page (Page 1). I don’t know why there are many repeats on your screenshot. 

What If wouldn’t there a preview page? (Page 1)

It looks like manually tracing would be best method in that case. 

Thank you very much for the answer.

Looks like they clipped pages 2-36. Duplicated them. Then rescaled the clips to create the preview page.

 

Does the Page 1 have vector drawing?

I exported the Page 1 as SVG then imported into an other software then I see there are no vector drawings. 

It’s like rasterized.

Here is page 1 imported in.  Rescaled so that the 10x10cm is exactly to dimensions. I also moved the page grid and text overlay to new layers. The issue is that the PDF is using clipping objects. Several hundred in fact. Selecting all the clipped paths and releasing the clips will result in complete non-sense. 

You could possibly use the grid layer to do a boolean intersection path effect on all the clipped paths similar to this example but I suspect Inkscape will cough up blood. 

https://inkscape.org/~COD/★intersecting-a-pattern-filled-object

Page 1 (the preview page) has vectors, but there are hundreds and they are clipped. It's probably easier to manually trace page 1 and scale to the desired size.

I would give my right index finger and maybe my thumb for an extension that would extract the paths inside of a clip (and delete the original clip). When I come across something like this - I usually delete it and start from scratch. Don't have the patience to figure it out. 

There is the destructive clip extension, part of the Mightyscape collection, but I didn't find it helpful in this case.

In this attachment,some of the paths I was able to extract. Used the node edit tool, select all, copy, then pasted off page. Hopefully it is scaled correctly. I included the original 10x10 proof. 

I noticed in this extraction that the belt is in one piece - but with different sizes. 

Ok - might as well go all the way with this. No idea if this is correct because I have no clue about clothing patterns but it looks correct. I compared it to the original PDF that was scaled correctly to the 10x10 cm "proof".  It is actually 4 pieces with belt. 

See attached. 

Edit: You might want to change the stroke size. I used 8 pixels. Each piece is a group of 7 different sizes. You will have to refer to the original PDF to figure out the different sizes. The shorten/lengthen lines you will have to figure out on your own. I have no knowledge of that at all. 

Better put back the shorten/lengthen cut lines back. Obviously that is important. 

See attached

Oof. That's a bit of work!

Whoever did that PDF worked their tails off. Over 500+ (lost count) clipping definitions. Then created 39 pages of scaled prints with IMG logos. I wonder what was used?  That wasn't done manually. LOL

I assume the pdf creator tried to protect the pattern in the document in this way. 

I don't think so. Just a large design that was split up to fit a certain size paper. No clue what software the Simple Sew company used. 

Edit - deleted the previous message attachments and just kept the last one.

I got the impression that the pdf was a reworking of a previous version (or versions) for logo updates and whatnot, and the last designer just bodged it together instead of doing it the right way.

Not sure about that. It is a very popular pattern via Google search.

The latest craze that actually make a lot sense:

 https://youtu.be/TsI2qGHP25Y?si=twA7frvHsetskozg 

https://youtu.be/VTzfOXXMSPM?si=9YbdvNfh51Z8pxBU

https://youtu.be/mWDnyNXBQk0?si=0aPF2piyOP1pNiFK

3rd one really instructive on how to calibrate Inkscape and the projector.

Playlist: 
https://youtube.com/playlist?list=PLlURmsXCNqyfp_syt7ZFtIydxteYIrmlB&si=gmlUzruh91APYgSU

I'm sure it's a popular pattern.

When I see logos and text covered by white rectangles and different/newer logos and text added in other areas, I know someone is cutting corners.

I didn't look that deep into the PDF. I was blown away by the 500+ clip definitions. When I put it in outline mode and saw that mess - did a facepalm. I usually just delete a file at this point and move on. I just got lucky and found the clip group that had the entire design on page 1. Then it was simple as using the node tool to copy all the nodes/paths. 

I generally don't use clipping in my use of Inkscape. Fusion doesn't recognize clipping. Only used clipping one time when v1.4 introduced the ability to split up an image using the shape builder tool. Great concept that I can use "maybe" on very rare occasions. 

Clipping is really only good for graphics/visual work.  ("If it looks good, it is good.")

I also do more work with the underlying geometry for CNC and similar, but do some graphics occasionally. 

I am amazed at the number of users that are "crafter/makers" that use Inkscape. I prefer to call them "CAD/CAM" users because that is exactly what they are. I participate in quite a few Reddit and FB "crafter/maker" groups and I amazed how different ways people use Inkscape. I was blown away by those previous YT videos I posted. Why didn't I think of that? 

I tried to use Affinity Designer but I keep coming back to Inkscape to actually get things accomplished "correctly". Inkscape does have long standing issues and as long as you understand them you can "getter done".