Hebrew to English Tech/Engineering Military / Defense history of Air Force Unit

wider context in Hebrew --
כאשר שחד מסדרם בזוגות גב אל גב

I cannot understand the meaning here of שחד in the rest of the sentence.
Here is a longer sentence in English with the Hebrew phrase inserted where it belongs.

Development of the target pages was performed manually when a special “technology” was developed; one soldier printed the pages at a murderous pace כאשר שחד מסדרם בזוגות גב אל גב (when שחד he arranges them in pairs back to back) and throws them like this into the developer, which was inside a gigantic barrel.

Any help is appreciated.

Thanks!